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General Collections Preservation Issues
Copyright 2003, Marc A. Williams


This article provides general collections preservation information. While not all of the information is applicable to every site, it gives broad treatment to a number of preservation areas.

Space Use

As a general rule, where possible, it is best to separate collections spaces from human use (offices, libraries, etc.) spaces. Ideally, they should not share the same building. If this is not possible, separating use by floor is suggested, with human use occurring on the uppermost floor, since heat for human comfort rises, potentially inadvertently causing excessively low RH levels for the collections if they are above human use areas.

An assessment of institutional space needs and space use should be included as part of the overall master planning process.

Drainage

Moisture infiltration into a structure is a major preservation concern for both the building and collections. Roof run-off, gutter overflow, and land run-off often collect near the foundation, soak into the earth and enter the building's basement and/or crawlspace. This can result in mold and mildew growth on architectural surfaces, warpage and distortion of wooden elements, and rotting of structural framing members. Addressing moisture infiltration must be considered one of the highest preservation priorities.

The grade of the land in the 10 feet nearest the building should slope away from the foundation on all sides in order to lessen the likelihood of moisture infiltration into the basement or crawlspace. While a few historic buildings still maintain appropriate grading, many do not. This can have resulted from many causes, including the raising of nearby roads or sidewalks, fill added near the building, and/or build-up from the decay of vegetation over time. In some instances, a slope away from the building can be created by minor regrading. In other situations, it may be possible to create swales to carry water away from the structure where sufficient natural slope away from the building does not exist. Archaeological issues can come into play when regrading, and should be considered prior to undertaking such a project.

The second line of defense is to install gutters and downspouts where they do not exist. The gutters must discharge sufficiently far from the building (10 feet) that the water is carried away from the structure. Installation of gutters and downspouts can be implemented easily and inexpensively, and can serve to significantly decrease moisture infiltration reducing the need for regrading.

If re-grading and guttering are not possible or effective, the alternative is to install perimeter drains. Generally, these consist of two separate drains, one near the surface of the ground that handles roof/gutter runoff and one near the bottom of the foundation approximately 4 feet or more below grade that handles water that soaks in from ground runoff. Often, these are tied to a storm sewer or drywell constructed for this purpose. A carefully installed water barrier is laid against the foundation and beneath the lowest drain to prevent water access into the basement/crawlspace. This type of project requires a significant amount of excavation near the foundation, potentially involving archaeological concerns, and is relatively expensive. However, it may be necessary if the other less intrusive and less expensive modifications are ineffective, or are not implemented.

Relative Humidity and Temperature Control

In a collection environment, hygroscopic materials such as wood, textiles, and paper always have some water chemically combined within their structure. The moisture content, as the amount of water is called, varies with the ambient relative humidity and temperature. Since the results are often most graphic with wood, it will be used as an example of the effect of fluctuating relative humidity and temperature. When the moisture content falls, wood shrinks across the grain. When the moisture content rises, wood expands across the grain. Wood can be considered to be dimensionally stable at all moisture contents along the grain direction.

Rising relative humidity causes an increase in moisture content and expansion across the grain, with a corresponding shrinkage when the relative humidity falls. Rising temperature causes shrinkage of wood and falling temperature, expansion. Within the environmental range encountered in Museums and historic houses, the effect of relative humidity changes is far greater than that of temperature. For conceptual purposes, a relative humidity change of 10% is roughly equivalent to a temperature change of 60 degrees F. Generally, temperature and relative humidity are inversely related. If the temperature increases, the relative humidity falls and vice versa.

In a totally unrestrained board that is rather narrow, the effect of expansion and contraction caused by fluctuating relative humidity and temperature may be minor. However, if restraint in any form is present, such as attachment to other boards, or if the board is wide, cracking, splitting, warpage, and veneer delamination can result. It is also possible to induce compression setting to wood, a permanent loss of dimension caused by an inability to expand when necessary. Restraint in historic objects is greatest in cross-grain construction - when one wooden member is attached to another and the grain directions are perpendicular to one another.

Wood is not the only hygroscopic (water-absorbing) material in historic collections. Finishes, adhesives, textiles, paper, leather and paint are all affected by fluctuating relative humidity and temperature. See Table 1 for details about different types of materials. Since all of these materials are components of complex objects, such as furniture, especially severe and damaging results can occur when one material reacts differently than other materials. For this reason, maximum preservation of furniture and most other collection items dictates that the relative humidity, and to a lesser degree the temperature, should be kept as constant as possible, not just during the course of a day, but from summer to winter as well.

In addition to problems with fluctuation, high temperatures accelerate chemical reactions. Since the bulk of degradation of historic objects is chemical in nature, high temperatures increase deterioration. High relative humidity levels (above about 65%) promote mold and mildew growth, as well as corrosion of metals. Low RH can lead to embrittlement of some types of materials, such as paper.

Historically, the generally suggested "ideals" for Museums have been 70 degrees F and 50% RH year round, although there are many circumstances where other levels should be chosen. This represents a temperature that is comfortable for humans and an RH level that is a practical compromise between the lows of winter and the highs of summer. It also assumes that specialized HVAC equipment is in use, and the building is specially designed or retrofitted to handle the deterioration risks introduced by environmental control.

The buildings at most small to medium-sized museums are equipped to maintain the temperature within a fairly narrow range, between about 60 and 90 degrees F, by utilizing heat in the winter and no control during the summer. A few have summer air conditioning, particularly in the more southern regions. However, control of the relative humidity is encountered too infrequently. This is primarily because these buildings are operated under the premise of human comfort, rather than that of object "comfort." In the winter, if the temperature is maintained at 70 degrees F, it is common to find relative humidity readings below 10%. During the summer, the relative humidity may exceed 90% for sustained lengths of time. Conditions such as these are responsible for virtually all of the cracking of solid wood, delamination and loss of veneers, distortion and cockling of paper, cleavage of finishes and paint, and mold and mildew growth on historic objects. Object "comfort" would dictate control systems based around more constant relative humidity, with less attention paid to temperature, exactly the inverse of what generally occurs in most smaller Museums.

"Ideal" environmental conditions that are suggested for collections preservation are likely to damage the building. During the heating season, in order to achieve a 50% RH level at 70 degrees interior temperature, it is necessary to add moisture to the air. The warmer the interior temperature and the colder the exterior temperature, the greater the amount of moisture that must be added. Since the amount of moisture in the air inside the building is much greater than outdoors, this moisture migrates through the walls towards the outside. At some point inside the wall, the dew point is reached and the moisture condenses on the wall materials, potentially leading to rotting wood, peeling paint, rusting metal, and spalling masonry surfaces.

Most of this damage occurs over long time periods and may not manifest itself for years. Nevertheless, it is ongoing, and a basic premise is that to ideally preserve collections, it is necessary to consider the building as sacrificial, needing to be significantly repaired or replaced at some time in the future. In a new Museum building, careful design and specialized construction techniques can allow a building to maintain "ideal" environmental conditions with minimal deterioration.

In a historic structure not designed in this manner, however, the building cannot be sacrificial and, therefore, a compromise must be reached that may not be ideal for the collection or the building, but will minimize deterioration to both. Often, this consists of holding the relative humidity within a fairly narrow range and allowing the temperature to fluctuate as necessary to help stabilize the relative humidity. By heating the air less during the winter, the natural RH level will be higher, and adding moisture to the air may not be necessary.

Each collection and building are unique and the specific solution chosen requires careful consideration of the needs of both. Generally, it is best to think of a target range of RH between 35%-60%, allowing the temperature to fluctuate as necessary to keep the RH more constant. Even greater stability of the RH, for example from 45%-55%, decreases the risk of damage to hygroscopic collection materials. Attempting to control both relative humidity and temperature significantly complicates mechanical control systems and makes them far more expensive to install and operate. If funding is limited, concentrate only on relative humidity control to maximize preservation.

The first step in environmental control is preventing moisture access to the building interior. The most useful reading for understanding the movement of moisture is the dew point. This represents the temperature at which 100% RH would be reached if the air was cooled (dew would form), thus the term dew point. This allows different RH and temperature readings in various rooms to be compared to each other in a standard manner. For example, 81 degrees and 49% RH sounds quite different from 73 degrees and 63% RH. However, both have the same dew point of 60 degrees, indicating the actual amount of moisture vapor in the air is the same. By viewing dew points, a better understanding can be gained of moisture migration from outdoors, the basement/crawl space and from one floor to another.

However, please recall that hygroscopic materials such as wood, paper and textiles are in equilibrium with the relative humidity (RH) and change dimensionally with changes in the RH. Constant RH is desirable for collections preservation. Since warmer air can hold more moisture, the same amount of moisture vapor in the air (same dew point) will have a lower RH in a warmer room and a higher RH in a cooler room, as in the example above.

Thus, it follows that in a building with a tightly sealed exterior envelope where the interior doors are kept open allowing free moisture movement within the building, the dew points should all be roughly the same, while the RH will vary inversely with temperature variations. The more even the temperature throughout the building, the more even the RH. However, this does not apply to a building with restricted moisture movement, such as closed interior doors, or that is open to the exterior environment (open windows).

Moisture infiltration comes from several different sources, presented below in rough order of importance:

1) roof and ground runoff penetrating the foundation;

2) infiltration of outdoor air with a higher dew point into the interior;

3) migration of moisture through the walls when the exterior dew point is higher than the interior dew point;

4) migration of moisture up from the basement/crawl space floor;

5) probably under only the most extreme conditions, if ever, the water table rising above the level of the basement/crawl space floor.

Control of the environment in collection areas must begin with control of moisture infiltration problems. Make sure grading around the building carries water away from the foundation. If necessary, re-grade or install effective gutters. Maintain a tight building envelope to minimize air exchanges with the outside and to prevent direct water access to the interior.

Further improvement of the environment can be effected with mechanical systems. Most off-the-shelf control systems are designed around temperature and not RH control. Therefore, it is important to consult with a competent HVAC engineer who fully understands the concept of controlling the environment for RH stability. Such an individual is not easy to find. Therefore, it is advisable to have a conservator as part of the team to guarantee that all parties fully understand the environmental control goals.

Stability of conditions is important on a daily basis, as well as seasonally. Therefore, generally it is better to keep the RH and T stable day and night, rather than turning up the heat when staff is present (forcing down the RH) and down when they leave (allowing the RH to rise). For this reason, it is not recommended that electric heaters be used in collection areas to temporarily heat them for human comfort. Similarly, air conditioners should be run continuously when needed, not shut off at night.

Opening doors and windows for air circulation and ventilation is not a good idea for collections preservation. This promotes more rapid changes of T and RH, as well as access for dirt and insects. In fact, tightening the windows and doors by the judicious use of weatherstripping and storm windows and doors will help to hold more even RH and T in both the summer and winter. Added benefits are savings in fuel for winter heating and summer cooling, as well as reduced amounts of dust and insects infiltrating the buildings.

Contrary to popular conception, a tightly closed building does not necessarily become unreasonably hot during the summer. In fact, if direct sunlight is blocked, it generally will be cooler throughout the day than one that has open windows. At night it will remain somewhat warmer than outside. Thus, the amount of temperature fluctuation will be reduced, as will be the relative humidity fluctuation. As an example, the Fremont, New Hampshire studio of American Conservation Consortium, Ltd. is a frame building of very tight construction. Windows and doors are kept closed, shaded, and are well insulated. During the month of July when no heating or cooling of the environment occurred, the lowest temperature logged on a recording hygrothermograph was 67 degrees and the highest was 73 degrees. The outside temperature ranged from 54 to 93 degrees. It is unlikely that the Museum buildings could be made as tight as the studio, and this narrow a range would not be achieved. However, a smaller range of fluctuation would result than is present currently.

An alternative worthy of consideration for heating systems is humidistatic control. A humidistat can be substituted for the thermostat on the heating system and set for around 50%. When the RH rises above this level, the heat is turned on, forcing the RH down. Thus, the temperature is allowed to fluctuate in order to more closely control the relative humidity. Clearly, this system can not compensate for RH levels that are too low, but it is not common for RH to fall below about 30% in unheated buildings. Thus, the RH range is kept between about 30% and 80%, instead of 5% and 80%. Allowing the temperature to fall below freezing is not a problem for most collection objects. If active plumbing is present, a temperature over-ride at about 38 degrees can be incorporated to prevent freezing temperatures from being reached. However, the over-ride may cause the RH to fall below desirable levels in very cold weather. Use of a humidistat might not be suitable for some exhibition areas, as the temperature can drop to levels that are uncomfortable for humans. However, it can be very effective for storage areas that are on their own heating system zone.

Generally, in most spaces, dehumidification is needed during the late spring, summer, and early fall. It is possible that some spaces will require dehumidification in the winter as well due to unusual moisture conditions. If the temperature is above about 60 degrees, portable dehumidifiers can be used where a central air handling system does not exist. Two factors are of extreme importance. First, all windows and doors will have to remain closed (this is recommended anyway to help stabilize the naturally-occurring environment) and the building envelope will have to be tightened, or the units will have to dehumidify all of the surrounding region in order to be effective. Second, portable units will have to be emptied conscientiously before they fill and shut off, or a large swing will occur in the RH levels when the dehumidifiers are not working, potentially causing damage to the collections. Attaching portable dehumidifiers to a drain is highly preferable to avoid repetitive emptying.

When temperatures are below about 60 degrees, conventional dehumidifiers will not function properly. Commercial portable dehumidifiers will function down to about 38 degrees. One manufacturer is Therma-Stor Products (1-800-533-7533), who offer the Hi-E-Dry product line.

An alternative for spaces that are below 60 degrees is heating the air slightly to bring the RH down to acceptable levels. A humidistat can be substituted for the thermostat on heating systems or portable heaters and set for around 50% RH. When the RH rises above this level, the heat is turned on, forcing the RH down. Thus, the temperature is allowed to fluctuate in order to more closely control the relative humidity. Clearly, this humidistatically controlled system cannot compensate for RH levels that are too low, but it is not common for RH to fall below about 35% in unheated spaces.

The use of air conditioning to control RH levels may, or may not, be feasible. As the temperature is dropped by the air conditioning, the air can hold less moisture, possibly raising the RH even though some moisture has been removed from the air. In addition, if the air conditioner is too large, it will not run sufficiently long to remove a significant amount of moisture from the air (called short-cycling), and will actually raise the RH of the space. Each specific situation needs to be tested and evaluated to determine if air conditioning can be used effectively to control RH. If so, it can be controlled by a dehumidistat in the same manner as a dehumidifier. If air conditioning can not be used alone to control RH, it can be used in consort with a dehumidifier. On most central air handling systems, dehumidification can be added within the air flow path of the air conditioning system.

Air conditioning also introduces potential problems with moisture gradients between the inside and the exterior of the building, similar to humidifying in the wintertime. This problem is most severe in hot, moist climates. Air in an air conditioned space is cooler and lower in moisture content than the outside air. Therefore, moisture will migrate through the walls from the outside toward the inside. Depending upon the specific conditions, it may reach the dew point inside the walls and condense on the wooden or metal structure of the walls. This can lead to rotting of the wood or rusting of the metal over extended periods of time. Keeping interior air-conditioned temperatures sufficiently high (generally, 78-80 degrees on very hot days) will prevent the dew point from being reached and eliminate the problem.

 

Table 1 - Possible Damage to Various Materials due to RH and Temperature

 

Material

Effects of RH Effects of T
Wood High - swelling, warpage, mildew

Low - shrinkage, splits

Fluctuating - delamination, splits

Preferred range: 40%-60%

High, low, or fluctuating - minimal effect

Preferred range: Below 90 deg. F

Finishes, paint High - bloom, mildew

Low - embrittlement

Fluctuating - cracking, delamination

Preferred range: 40%-60%

High - softening, accelerated aging

Low, fluctuating - minimal effect

Preferred range: Below 45 deg. F

Metals High - corrosion/rusting

Low, fluctuating - no effect

Preferred range: Below 35%

High - increases rate of corrosion

Low, fluctuating - no effect

Preferred range: Below 90 deg. F

Glass, ceramics No effect No effect
Textiles High - mold, mildew

Low - possible embrittlement

Fluctuating - possible distortion

Preferred range: 40%-60%

High - accelerated aging

Low, fluctuating - minimal effect

Preferred range: Below 45 deg. F

Paper, photographs High - mold, mildew

Low - possible embrittlement

Fluctuating - possible distortion

Preferred range: 30%-50%

High - accelerated aging

Low, fluctuating - minimal effect

Preferred range: Below 45 deg. F

Leather, skin High - mold, mildew

Low - possible embrittlement

Fluctuating - possible distortion

Preferred range: 40%-60%

High - accelerated deterioration

Low, fluctuating - minimal effect

Preferred range: Below 45 deg. F

Stone No effect No effect
Ivory High - swelling, warpage, mildew

Low - shrinkage, splits

Fluctuating - delamination, splits

Preferred range: 40%-60%

High - accelerated aging

Low, fluctuating - minimal effect

Preferred range: Below 45 deg. F

 

An alternative method of controlling the RH that can be considered is the use of electronically controlled fans to move air into or out of the building depending upon the difference between the interior and exterior. Such a system is driven by a computer and RH and T sensors. If, for example, the interior RH is too high and the exterior RH is lower, air would be exhausted from the building and outdoor air brought in. However, if both the interior and exterior relative humidities are too high, this type of system can do nothing to bring the RH within desirable levels. The system can work in reverse. If the interior RH is too low and the exterior is higher, outdoor air can be brought in. Fine filtering of air entering the building is required to prevent excessive entry of dust and dirt.

This concept of control is complicated by the fact that RH levels change depending upon the temperature of the air. Colder outdoor air may have a higher RH, but when it is warmed once inside, its new RH may in fact be lower than the interior air. Use of dew points instead of relative humidities eliminates this problem. Then, when the dew point of the air outside is lower than the dew point of the air inside, running the fans will always reduce the amount of moisture inside the building. Due to the complex nature of the required measurements and calculations, a computerized control system is required.

Relative Humidity and Temperature Monitoring

Every building has unique needs and solutions for control of the T and RH. However, in order to make intelligent suggestions on environmental needs and improvements, the existing environment must be monitored for a continuous period of at least a year. A comprehensive program of monitoring the temperature and relative humidity allows thoughtful steps to be taken in controlling the collection's environments. They will contain signals of whether dehumidifiers are needed and when they need to be turned on; if and when air conditioning is required; and may serve to point out problems with drainage, leakage or water infiltration before they would otherwise be noticed. Without monitoring, environmental control efforts are just guesses, with no way of determining if the desired effects are actually occurring.

In general, inexpensive manual monitoring systems require more human involvement than high-tech automated ones, which require more money. Therefore, if staff time is available and money is not, begin with a manual system and possibly seek funding for a less labor-intensive system in the future. Take manual readings in each area that contains (or is projected to contain) collections in storage or exhibition. It is also helpful to take a reading outside the building to record the exterior conditions and to note where the readings are taken in each room.

A hygrometer/thermometer that is a good compromise between accuracy and price is made by Airguide. This digital unit also records maximum and minimum T and RH. Several suppliers sell it for prices ranging from $40-$70, but it is also available as a service to the Museum community from American Conservation Consortium at our wholesale cost of approximately $20 each. Mount them on an interior wall or surface away from heat ducts or radiators, one per room, at a vertical elevation that matches the majority of the collection items, generally about 2-3 feet from the floor. Record the maximums and minimums of RH and T on a chart once a week, preferably on the same day of the week. This data can be entered into spreadsheet or other computer software to produce charts covering an entire year.

A more sophisticated monitoring option is the use of recording hygrothermographs (cost: $500-$800 each). These maintain a constant record for a period of a week, allowing detection of daily variations, and require attention only to change the charts and to be calibrated periodically, generally every 6 months. Place them in the room at approximately the same height from the floor as the bulk of the collection items. Since temperature readings vary with height, so will the recorded readings vary. Every six months, the hygrothermographs should be checked for accuracy with a battery or sling psychrometer or a highly accurate digital hygrometer. If possible, purchase units that allow switching between daily, weekly, and monthly cycles.

An alternative "automated" system is the use of data loggers. These devices are about the size of a deck of cards and contain a battery that gives them an extended life. They take T and RH readings at a user-selected interval, for example, every 10 minutes, and store them internally on a microchip. About once a month (or less frequently if desired), the data collected is down-loaded into a personal computer, using a software provided. Various charts and graphs can be generated from the collected data.

The advantage of this system is that the data collected can immediately be manipulated into forms that give useful information. For example, a chart of weekly averages can be generated for a full year cycle. To do this with recording hygrothermographs would require somewhat tedious examination of fifty-two weekly charts and manual averaging and recording of the readings. A logger costs about the same as a recording hygrothermograph and they would be dispersed one to a collection area as well.

A less expensive data logger is made by Onset Computer Corporation (508-759-9500). This logger sells for about $95 and is quite tiny, being about the size of a small box of matches. Called the Hobo H8 RH/Temp/Light/External, this logger is not quite as accurate as the more expensive loggers, but is fine for the needs of collections within historic buildings. It is an excellent alternative that allows for sophisticated environmental monitoring on a limited budget. As an added bonus, the logger has a light sensor which can be activated to record light levels. Onset also sells other variations on this logger, including one which is weatherproof for outdoor locations.

A final monitoring alternative is the use of a data acquisition package tied to a computer. It consists of T and RH sensors connected by wires to a hardware signal processing box, which connects directly to a computer. This allows real-time readings of temperature and relative humidity to be displayed on the screen. Additionally, the readings are saved to computer disk and various graphs of historic data can be printed.

One such system is designed as a weather monitoring system (called the Observer Meteorological Station). The base unit includes two temperature and relative humidity sensors on 50 foot cables, three additional temperature sensors, the signal processing box, computer cables, and DOS or Windows software. The price is in the $500-600 range. If there is sufficient interest from the Museum profession, the manufacturer, Fascinating Electronics, can redesign the basic system to allow up to 10 pairs of RH and T sensors. Additionally, the Observer Meteorological Station can be used to control environmental systems. While these control capabilities are already built-in, some engineering would be necessary to allow them to meet the specific needs of Museums, with relative-humidity-based control requirements.

The design, purchase (of both the system and computers), installation, set-up, and evaluation of monitoring methods is fundable through the Conservation Project grant program of IMLS (See the Fund Raising section of this report). The monitoring time can be used as part of the Museum's match for an IMLS-CP grant if the project is properly designed.

A complete year of records allows intelligent steps to be taken in controlling the collection's environments. For this reason, assembling the readings should not be taken as an exercise in record-keeping. The readings must be examined and compared, and used as the basis for decision making. They are probably the most important tool to be used in the preservation of the collection, and, in fact, for the preservation of the building itself.

Readings obtained from a monitoring program must be analyzed. If desired, an outside consultant, such as this collections assessor, can be contacted for assistance. As mentioned previously, the goal for RH is 35-60%, with temperature control of relatively minor significance. If tighter RH ranges can be obtained, even less deterioration will occur.

Light

Light destroys the natural or maker-applied colorants in wood, dyes, finishes, paints and fabrics. Textiles and paper are weakened, possibly to the point of disintegration. In severe cases, light can degrade the cellular structure of wood. All of these changes are irreversible and permanent. The amount of damage from light depends upon the wavelengths of light present (sunlight has them all), the intensity of the light and the length of exposure. Reducing any or all of the three will have benefits. However, only total darkness will eliminate the threat of light damage. Therefore, light control can be facilitated by eliminating the most damaging wavelengths (UV, violet and blue), reducing the intensity as much as possible and shortening the length of exposure.

In addition to direct effects, light can raise the temperatures of individual objects, as well as the temperature of the room itself. This causes a corresponding drop in the relative humidity levels, or in the case of wood and other hygroscopic materials, a drop in their moisture contents. When the light is no longer on them, temperatures drop and relative humidities and moisture contents rise. Thus, a daily cycling of T and RH occurs, with a great propensity for damage to surfaces, such as veneer, finishes, gold leaf and paint.

Several factors influence the amount of daylight falling on the collections. One factor is the time of day. In the morning, an east room may have 25 times as much light present as in the afternoon. Thus, when readings are taken, they may not be at the time of maximum light. Similarly, sunny days create much higher readings than overcast days. Even a cloud passing over the sun dramatically changes the light level reading.

Another factor is the distance from the light source, either natural or artificial. The law of reciprocity states that light levels fall off with the square of the distance from the source. A light level of 1000 lux of indirect light at a single window will be approximately 100 lux at a little over 3 feet into the room and around 10 lux at 10 feet into the room. This is true also of artificial light sources. Additional windows or light sources in the room each cumulatively affect the actual reading. If objects are displayed on walls near windows or near artificial lights, extremely high levels of light damage may result. Simply moving the objects away from light sources can dramatically reduce the amount of damage.

Control of light can be accomplished in several ways. The simplest is to block off the windows in an exhibition or storage area. This can be done with solid panels, black-out cloths, shades or shutters. It is especially important to exclude direct sunlight, although indirect light is still highly dangerous.

A second technique is to reduce the intensity of the light by filtration. This involves the application of a film or plastic sheet to the window or its opening that filters or reflects a large percentage of the light, in essence acting as sun glasses for the window.

A third option that is related to this is the filtration of the UV component of the light. This can be combined in the same film or sheet as intensity reduction. A final method is to remove all light-sensitive objects from areas or rooms that are too bright.

The goal of light control is to remove all of the UV and reduce visible light levels to less than 150 lux (50 lux for extremely sensitive items such as paper and many textiles). When buildings are not open for visitation (e.g. mornings and evenings, as well as holidays and during the winter), exhibition areas should be completely dark. Storage areas should be dark all the time. Clearly, the control techniques chosen must integrate with the aesthetic interpretation of the buildings. However, it is important not to let such issues become a stumbling block for doing something to control light.

It would be useful to have a more definite idea of how fast light damage is occurring. This can be accomplished by use of blue wool standards. These are cards containing a number of dyed blue wool patches of known rates of fading. Cards are dated and placed in various appropriate locations. After a set length of time, they are examined. Ideally, there will be no noticeable fading when compared to a fresh card that has been kept in the dark. If fading is present, the amount can be estimated by which of the patches show signs of fading and which do not. The most sensitive patch is roughly equivalent to the sensitivity of paper, textiles and wood dyes. The standards are available from conservation supply houses.

Blue wool standards do not give an indication of the amount of light falling on an object, nor the maximum intensities, but rather the cumulative effect of the light. Use of the Onset H8 data logger previously discussed would track the actual light levels over time, including maximum intensities. This data would reside in digital form for easy export to spreadsheets, allowing custom manipulation of light level data.

The nature of long-term static displays places unique deterioration stresses on the objects they contain. Generally, the objects cannot be rotated easily on and off exhibit. This subjects them continuously to a relatively harsh environment, especially those materials sensitive to light. Where possible, such items should be rotated with other items, or, in the case of upholstery, seasonal covers can be alternated.

It is important to keep light levels throughout the building uniformly low. In this manner, the visitor's eye can adjust to the lower level. If levels alternate between low and bright, the human eye cannot adjust quickly enough to the changes and visibility will be impaired greatly. In addition, visitors often look towards a window when in a room. Lower light levels at the window will reduce the blinding effect, and actually allow the room contents to be seen more clearly.

The simplest light control method is to install pull-down window shades. If these are the only type of light control used, two shades should be installed on each window. The first is a room darkening shade, preferably in a white color to reflect heat. This shade should be kept closed whenever people are not in the room, especially when the building is closed for the season. The second shade should be visible light filtering (90% or more effective) and UV filtering (near 100% effective) mylar. This shade should be pulled whenever people are present. In this manner, the UV light will be excluded at all times and no more than 10% of the visible light allowed when people are in the room. Otherwise, the room will be dark. Exposure to light will eventually degrade the shades themselves, and they will have to be replaced periodically. Depending upon the quality and nature of the construction of the shades, this could vary from about 5 to 25 years.

Alternatively, plexiglass interior storm windows could be installed instead of the mylar pull-down shades. Of course, they should also filter at least 90% of the visible light and all of the UV light. Room darkening shades would still be used in consort with the plexiglass. If the plexiglass is installed in as airtight a manner as possible, it will serve to reduce environmental fluctuations as well.

Accessioning/Deaccessioning

When an object is accepted into a museum collection, it attains a status that is different than it had when in use in the donor's house. It is no longer acceptable to handle the object without taking proper precautions. Certainly, the object can not be used. Proper display and storage must be provided to the object, as well as competent conservation care when required. In essence, each object must be placed on an imaginary pedestal and granted an unique and special status. This applies to all objects, regardless of their economic value, cultural significance or aesthetic beauty.

Preservation of the collections is a legal custodial responsibility of the institution. Time frames for preservation are hundreds or even thousands of years. This can be difficult to comprehend fully from our current societal perspective of planned or natural obsolescence, where an object's lifetime may be only a few years. Therefore, mental adjustments may be necessary to allow future generations to appreciate their cultural heritage. It is important that all members of the Board recognize this long-term perspective, and the degree of effort required to properly preserve the collections. It is better to correctly preserve fewer items than to allow a larger collection to suffer unnecessary degradation. Thus, carefully thought out and planned deaccessioning can actually be an effective preservation tool. Funds generated from deaccessioning can be used to obtain more appropriate collections objects and to fund collections preservation needs of the remainder of the collection. However, these funds should not be used for any other purpose. To do otherwise would be considered a violation of Museum ethics.

The storage and display capacity of many institutions is limited. Tightening up the requirements for accepting donations and evaluating objects already in the collections for possible deaccessioning are good methods of addressing this problem. Clearly, being restrictive on donations can be a politically sensitive issue. But the institution must resist the temptation to accept items it does not want in order not to hurt the donorís feelings. A clearly written collecting policy is the best method of assuring fairness, and generating understanding on the part of the donor. The institution can not afford to care for an unlimited number of objects. Be sure to obtain a letter of donation for all objects, specifically indicating that the institution can do whatever it wishes with the objects, including sell or dispose of them.

Generally, at most smaller institutions, an accessioning system consists of the year of donation, followed by a dot, then the number of donation or purchase that year (1996.23 for the twenty-third item obtained in 1996). The recommended procedure for applying accession numbers to objects is to paint a small patch (approx. 1/2" x 1" or smaller) with Acryloid B-72 (an acrylic resin made by Rohm & Haas), which will dry transparently. This acts as an isolating barrier. The number can then be painted on the dried B-72 in red, black or white artists' acrylics (depending upon contrast with the object's color) with a very fine brush. Apply numbers to unobtrusive locations, such as backs, bottoms, or undersides. On large objects, such as furniture, be sure that the number can be seen without having to move the object. The bottom side of a rear foot, for example, is a good location.

Do not use these methods for absorbent materials such as paper, textiles, leather, etc. Paints and coatings can stain the object. The safest method for these objects is to use string tags, with the tag tied loosely around a stable area of the object, and not taped or stapled to it. The tags should be marked either with a typewriter or pencil. For some object types, such as books or archival materials, the number can be written inside the fly leaf at the front or on the back in pencil. On framed prints, it can be written on the mat. For textiles, the number can be written on a cotton tag with a laundry pen or other insoluble marker, and the label sewn onto the fabric in a stable location with cotton thread. If any uncertainty exists about the safety of applying the accession number for a particular object, consult with a Museum registrar at a large institution or with a conservator.

Exhibition Issues

When designing exhibitions of collection objects, several approaches can be taken. One of the most common at local historical societies utilizes cases, shelves or cabinets full of varied artifacts. Objects are not grouped by date of manufacture or by use. Generally, very little or no information is given in the displays on the function of the objects and how they fit into a broader cultural perspective. This component may be added to a degree by a guide, if one is present, based upon his or her personal knowledge. For want of a better term, this approach to display will be called warehousing. In its most extreme form, warehousing involves storage of large volumes of objects with no attempt to display them.

Several other alternatives of display exist. For the sake of this report, they are given the names theme display and historic display. Exhibits built upon the theme concept focus themselves on a specific subject, such as kitchen life in the 1890's or the role of women in the timber industry of the early 20th century or changes in cabinetmaking tools from the 18th through 20th centuries. Displays include objects and extensive signage describing the objects, as well as other pertinent background information. The advantages of theme display are increased learning potential by visitors, and the ability to rotate exhibits on different subjects.

Historic display attempts to create the actual appearance of a specific room at a specific time in its history, usually around when it was first built. In its purest form, historic display uses research to determine the exact colors or surface treatments in a period room, and re-exposes or re-creates them. This is complemented by displaying the actual furnishings used in the room at the period. Mount Vernon, George Washington's home, is an example. Most historic displays are not so fortunate to locate and display original furnishings, so other items of the period that would be appropriate are used. Sometimes, these can include faithful reproductions.

Any form of display can be utilized by the Museum to meet its own needs. However, it is important that the choice be made consciously, and not by default.

Most collection objects are on long-term display. In addition to placing the highest level of deterioration risk on the objects, long-term display creates exhibitions that are essentially static and do not change. This display approach requires less staff time in the organization, preparation and installation of exhibits. However, repeat visitation may suffer and there is a risk that objects will become forgotten or "lost" in the collection.

Future staff will have no history for them, and much of the oral tradition currently surrounding them will disappear. Therefore, it is critical that as much as possible be written down about each object, especially if it has a local history and the person who gave/sold it (or their family) is still around. Similarly, the stories told by Board members and guides should be collected together, edited, and written down for use by future staffs. This has the additional benefit of allowing a more consistent interpretation by formulating a "standard" presentation.

The nature of the materials used for the supports, shelving, and cases is very important for collections preservation. A very good basic treatise on this subject is found in the book Conservation Concerns: A Guide for Collectors and Curators (Konstanze Bachmann, Ed., Smithsonian Institution Press, 1992), pp. 23-28. Some very general concepts will be presented in this assessment, but this book and other relevant sources should be consulted for more detailed information. Comments about exhibition materials also apply for storage.

In general, many materials that have been used traditionally to construct display furniture (this term is used as a convenience to refer to all types of shelving, cabinets, supports, etc.) themselves produce harmful vapors. Most woods are acidic and continue to off-gas harmful volatiles throughout their lifetime. These are particularly dangerous to metals, paper and textiles. Direct contact of wood with collections items, as well as containment of collections within containers of wood, present the greatest risks. It is not possible to completely seal wood with paint or varnish to prevent this damage risk. Some types of paint even promote the production of additional harmful vapors. Therefore, generally, wooden display furniture should not be used for sensitive collections objects.

Composite wooden materials, such as plywood, particle board and medium-density fiberboard have an additional concern. They are held together with adhesives that contain urea-formaldehyde. Throughout their lifetime, they continue to volatize formaldehyde, which can damage collections objects. If possible, composite wooden materials should be avoided in collection areas.

Generally, the safest display furniture is made of steel. In the past, the recommended coating has been baked sprayed enamel. Two potential risks exist with new baked enamel paint. First, it is important that the baking be done properly, or the paint could release large quantities of harmful solvent volatiles. Unfortunately, it is not possible to easily determine if baking was done correctly. Second, even if done properly, smaller quantities of solvent volatiles continue to be released over time. These solvents can attack and deteriorate sensitive collection objects. Generally, if the paint was applied 2-3 years ago or more, its off-gassing of solvents should be negligible. Older steel furniture with original paint has completed this off-gassing process, and does not pose a threat to collections. However, if it has been recently re-painted, the problem once again exists.

A more recently developed paint application technique that appears to be safer for collections is powder coating. The paint is applied dry and is held to the metal by electrostatic charge prior to baking. Since solvents are not used in this process, there is very little risk that harmful components will be given off once in the Museum environment.

Less traditional materials that can be used for storage furniture with a reduced risk of damage are polyethylene and polypropylene. However, it may be hard to find ready-made furniture, since this is a less common use of these materials. Nevertheless, they can be used for custom or in-house construction.

The wooden cases used for exhibition of many of the collections pose preservation problems. All interior wooden surfaces should be sealed with a minimum of three coats of white pigmented shellac (painted) or three coats of unpigmented dewaxed [dissolved in denatured alcohol from flakes] shellac (transparent finish). Allow one to two weeks drying time for the solvent to adequately evaporate. Also acceptable are three coats of polyurethane varnish, but these require a drying time of at least a month to release trapped solvents in them. Coating application does not prevent off-gassing of harmful components, but slows it to a level that is probably safe for most materials.

As an additional precaution, line the bottoms/shelves of the cases with acid-free mat board to absorb acidic vapors that may off-gas from the wood (unbuffered if silk or wool will contact it; otherwise buffered will absorb more acid). On a regular basis, replace the mat board once it loses its acid-free status, probably every 5-10 years for unbuffered and 10-50 years for buffered, depending upon the specific environment inside each case. Be cautious about using modern fabrics or other materials inside cases, as these themselves can be acidic and damage collections. If possible, test the acidity of fabrics before using them (the conservation suppliers have test materials/supplies). It is possible to use acid-free mat board as the visible case bottom without any covering. Acid-free mat board is available in colors to provide more variety in designing exhibits.

If wooden collection furniture is used for display or storage, the application of coatings to seal the wood is not recommended, as this alters the furniture in an irreversible way. Ideally, paper, photographs and textiles should not be stored in wooden objects, including in drawers. If this must be done, line the bottom of shelves or drawers with buffered acid-free mat board. If possible, line the backs of drawers and other enclosures with buffered acid-free mat board as well. Do not attach the mat board to the wood, but allow it to free-stand. Additional protection will be provided if textiles, paper and photographs are first placed in acid-free boxes and the boxes are then stored in the collection furniture.

Case precautions become more significant if the cases will hold sensitive objects such as paper and textiles. Cases for wooden objects, for example, can adhere less stringently to these suggestions. However, if cases will hold a combination of object types, the most sensitive type dictates the needs for the case as a whole.

The use of properly designed cases to display objects has a number of benefits. The most obvious one is security, preventing the handling or theft of collections. In addition, cases reduce the exposure of objects to dust and dirt. If they are fairly tightly sealed, they act to reduce the extent and rapidity of environmental fluctuations, helping to minimize resulting damage to objects within them. However, an important consideration is the types of materials that are exhibited together within a case. Certain types of collection materials can cause degradation to other types of collections. For example, wooden objects could cause acidity damage to paper objects by off-gassing within the case. Similarly, off-gassing of wood can corrode lead and other metals. It is particularly important to include acid-free mat board in cases with dissimilar objects to help absorb vapors. Also available are special compounds sold by the conservation suppliers that absorb a wide range of harmful volatiles which can be enclosed in cases to provide additional protection.

If materials within a case are the same or similar, such as paper and textiles exhibited together, the cases can be of tight construction, assisting with environmental stability and reducing dust exposure. If the collections may be harmful to one another, such as wooden objects with paper, textiles or lead, the cases should not be tightly sealed. In fact, care should be taken to provide adequate ventilation. This can be in the form of holes in discrete locations, or can be as aggressive as small fans forcing air circulation. Holes or other openings can be covered with filter paper (coffee filters will work) or another fine-pored material to reduce dust infiltration.

Use of Objects

Use of objects hastens deterioration. This is in addition to deterioration that occurs due to the environment and natural causes. Less use produces less deterioration, but still causes more than no use. Deterioration from use can be sudden, such as breakage of ceramics and glass or cracking of wooden furniture members, or it can be gradual, such as wear to furniture finishes and carpets or corrosion of metals from finger prints. Additionally, the message conveyed by use of accessioned collection items is not one of preservation, and this can be confusing to visitors and staff.

When an object is accepted into a museum collection, it attains a status that is different than it had previously. It is no longer acceptable to handle the object without taking proper precautions. Proper display and storage must be provided to the object, as well as competent conservation care when required. In essence, each object must be placed on an imaginary pedestal and granted an unique and special status. This applies to all objects, regardless of their economic value, cultural significance or aesthetic beauty.

Handling of collection items adds greatly to deterioration. Hands contain salts, acids and oils that will stain, corrode and discolor collection items. Metals, textiles, paper, leather, furniture finishes, bone and ivory are particularly affected. Collection items should not be handled unless necessary for maintenance, display arrangement or routine dusting. White cotton gloves should be used whenever handling collection items, with the possible exception of glass and non-porous ceramics, as these items may be too slippery to use gloves.

If collections will be used hands-on or for interpretation, be consciously aware that their lifespan will be reduced. This can not be prevented. The institution does have the right to use collections for its personal needs or educational goals, but must be willing to accept the deterioration consequences. Generally, it is best to deaccession these objects into a special classification such as "historic utilitarian objects" so that they will not be confused with true collections for which the institution has a responsibility for preservation. Some of the collections items are located where visitors can handle or touch them, or possibly even steal them. Additionally, they may be hit or bumped accidentally. Where possible, move accessible items or redesign traffic flow. Where objects can not be moved out of handling range, prominent "Please do not touch" signs can be installed. Probably the best defense is the vigilance of the guide staff. Do not allow groups to be larger than can be watched carefully by the staff. Make sure that all guests stay in the same room as the group on guided tours. Include a request when greeting visitors that they do not touch

objects. If objects are historically irreplaceable, they should be moved to a secure display location, such as a locked display cabinet, to prevent both damage and theft.

Storage

Where possible, it is best to separate collections spaces from human use spaces. Ideally, they should not share the same building. If this is not possible, separating use by floor is suggested, with human use occurring on the uppermost floor, since heat for human comfort rises, potentially inadvertently causing too low RH levels for the collections. These comments apply when using heat-only environmental control methods. Obviously, with sophisticated HVAC systems, the environments on any floor can be independently controlled to very tight tolerances. However, unless proper alterations have been made to the physical envelope surrounding the controlled space to allow it to handle environmental stresses, there is risk of damage to the building. If a building is not heated at all, it is not critical whether human use is above or below collections.

Room-within-a-room construction minimizes the risk of unstable environments. A separate free-standing structure is built within the space. The walls, floor and ceiling are insulated with a minimum of 6 inches of fiberglass insulation. A vapor barrier (6 or 8 mil polyethylene sheeting) is placed on all interior surfaces. A single door of sufficient size provides access to the space. The door is well-insulated and well weather-stripped. The room is built so that it does not touch the walls or ceiling with approximately two feet of clearance, allowing air circulation around it. If needed, small fans can create air circulation inside the room, improving uniformity of conditions and reducing the likelihood of mildew growth.

While conditions outside the room will still vary on a daily basis, inside the room, very little change will occur. Seasonally, there will be a gradual temperature shift, but the relative humidity should remain within a fairly narrow range of about 45%-65%, provided that the space containing the room-within-a-room is not heated. This is accomplished without the use of any mechanical systems. Obviously, proper HVAC system design and installation can improve further upon the passive control methods. If the room-within-a-room is constructed in an attic-type space, full ventilation of the attic is recommended, enhanced if necessary by ridge and soffit vents or exhaust fans.

The nature of the materials used for the supports, shelving, and cases is very important for collections preservation. These issues are the same as for exhibition and have been addressed above in the Exhibition section.

Overall responsibility and policy for the storage areas should be clearly defined, written down, and made known to all relevant staff. Otherwise, well-intentioned staff may be working at cross-purposes. Included in the policy document should be procedures for the protection of the stored collections, such as routine maintenance, cyclical maintenance, environmental settings, light levels, handling procedures, regulations for use (for example at off-site lectures), and some sort of tracking system to know where objects are located, especially if they leave the storage area. General suggestions for storage follow.

1) Stacking of objects is not recommended. If absolutely necessary to do so, a padding material, such as mover's blankets or thin Ethafoam (1/8" polyethylene foam), should be placed between objects. Objects must not be too closely packed, touching neighboring objects. This can lead to abrasion damage.

2) Collections items should be raised off the floors at least 3" and ideally 6". In the event of a disaster, including water from fire fighting, considerable damage can be avoided if the objects are not sitting in a pool of water.

3) Pad beneath items on shelves. 1/8" Ethafoam works well and comes in long rolls of appropriate width. Try not to crowd items, and do not stack them unless they are adequately strong and are padded between items.

4) Closed metal storage cabinets are suggested for the glass, ceramics and other breakable items. Pad the shelves with 1/8 inch Ethafoam or another suitable material. If items are stacked, pad between each piece with Ethafoam or several layers of tissue. Bolt the cabinets in place so they will not fall over in the event of an earthquake or other vibration. If open shelving must be used, install a 1" high lip on all shelving edges to prevent items from "walking" off the shelves.

5) Light-weight polyethylene dust covers should be placed gently over unprotected items in storage. A source of supply is Elkay Products Co., 35 Brown Avenue, Springfield, NJ 07081 (201-376-7550). They can be ordered in sizes as large as sofa size and used to cover a number of collection items at once. Items on open shelves should be covered as well.

6) Framed items in storage should be grouped together in vertical storage with separator pieces of mat board or acid-free cardboard between the frames. Acid-free cardboard boxes can be used as containers.

7) Quilts, coverlets, rugs, and other large, flat textiles should be stored horizontally on a rolled rack. Carpet tubes (often available for free from carpet installers) covered with polyethylene or Mylar, followed by acid-free tissue, will work well for support. Place a dust cover over the rolled textiles.

8) Use acid-free boxes for items stored in boxes. Do not crowd objects and use padding between items. This is especially true of textiles.

9) Refer to the NEDCC notebook mentioned previously for storage suggestions for paper and photographs.

Obviously, a major factor in designing and organizing storage areas is the size of the collection. For this reason, determination of the collecting philosophy and deaccessioning policy are critical factors that need to be addressed first.

Routine and Cyclical Care and Maintenance

Generally, care and maintenance falls into two categories. Routine maintenance is the day-to-day procedures necessary for preservation, as well as for aesthetic presentation. It includes dusting, vacuuming, and cleaning of objects. Generally, routine maintenance is provided by staff. Cyclical maintenance occurs less frequently, yet still on a regular basis. Included are furniture waxing, moving objects for thorough cleaning behind them, cleaning inside of cases, and polishing and coating of metals. Cyclical maintenance can be done by staff or contracted to a conservation firm. Schedules and procedures for both routine maintenance and cyclical maintenance must be written down to guarantee continuity.

To guarantee continuity of care, the written Routine Maintenance Plan should outline maintenance procedures, materials and frequency of care, including objects in storage. Once such a document has been created, it should be reviewed with each person responsible for object care. When new people join the staff, they should be trained in proper maintenance and care of collection items following the guidelines in the Plan.

Dusting

The first line of defense against dust and dirt is to prevent their access to the building. General procedures that assist in this include sealing holes and gaps to the outside, keeping windows and doors closed, and providing mats at access doors to allow visitors and staff to wipe their feet when entering the building. Clean the mats often.

It is possible that stand-alone dust filtration units can aid in the collection of dust within the building. Honeywell and Bionaire make units that incorporate HEPA filters and should be a good choice (check at Sam's Club or similar stores for good prices). Again, in order for air cleaners to be effective, the building must be as tightly sealed as possible, or they will be trying to filter all the air in the region. Obviously, filters need to be changed on a routine basis, and this procedure should be written into the Environmental Control Plan.

Dusting may be done with soft cloths, either dry or moistened very slightly with distilled or de-ionized water to hold the dust. A misting sprayer directed at the cloth, not the object, works well. Do not use polishes or dusting aids. An alternative cloth is the Dust Bunny. It is woven of two different fibers that, when in association with each other, create a static charge and hold the dust to the cloth. The cloths are reusable, washable and available from the New Pig Corporation (800-468-4647). Be sure to change them as they get dirty.

When moving collection items to allow dusting, wear clean cotton gloves to prevent corrosion and deterioration caused by hand salts, oils and acids. This is extremely important for metals, paper, and textiles. However, for slippery objects such as glass and glazed ceramics, gloves should not be used. Do not dust surfaces with active cleaving and lifted paint, finishes, or gesso and gold leaf. These cleaving problems must be handled by a conservator.

Vacuuming

The major concern in vacuuming is the risk of nicks, abrasions, dents and scratches on the bottom several inches of objects resting on or near the floor, in addition to hitting objects with the vacuum body. Pad all hard metal or plastic parts of vacuuming attachments. Do not vacuum period textiles, including costumes, or other types of fragile objects unless instructed to do so by a conservator.


Cyclical Maintenance

General Cleaning

Staff may not be able to thoroughly clean many objects. These include fragile pieces, such as cracked or cleaving surfaces, gilt objects, textiles, paper and other delicate surfaces. Additionally, other objects cannot be moved due to their size or delicacy, and cleaning behind and under them is impossible. On a periodic but scheduled interval, the collection should receive in-depth cleaning. An additional benefit is the ability for the collections items to be inspected closely for signs of deterioration. Perhaps once every 1-3 years is sufficient, but the exact frequency must be determined for each area and written into the Cyclical Maintenance Plan. Case and cupboard interiors should be cleaned on a regular basis as well.

The frequency of cyclical maintenance will depend upon the needs of each specific building, and the nature of individual collections items. Additionally, if environmental systems are altered, the frequency of cyclical maintenance can be affected. For example, if better dust filtration can be provided and integrated pest management can be improved, the interval may be able to be extended. If staff time is too tight to allow cyclical maintenance, this service can be contracted with a conservation firm.

Some types of collection objects that do not respond to dusting can be "wet" cleaned. More securely attached dirt on non-absorbent surfaces in good condition may be removed with surfactants which are mixed in a dilute (approximately 1%) solution with distilled or deionized water. Common types are Orvus Liquid, Triton X-100 and Vulpex. If a local source can not be found, surfactants can be ordered from Conservator's Emporium, 100 Standing Rock Circle, Reno, NV 89511, 702-852-0404. A small spot in an obscure area is tested with the solution on a cotton swab. All areas that appear to be a different surface or material must be tested separately. If the solution does not damage the test area, it can be used to clean the piece. A soft cotton cloth or pad is dampened slightly and rubbed over the surface. Avoid excessive wetting of the surface, which may cause the types of damage associated with water. The cleaned surface should be wiped with a soft cloth dampened slightly with plain distilled or deionized water to remove surfactant residues, followed by a dry soft cloth. Finished wooden surfaces that show deterioration or bare wood should not be cleaned with water solutions of surfactants and should be referred to a conservator.

Dirt on wooden surfaces in good condition that does not respond to surfactant cleaning may be removable with organic solvents. When using solvents, it is a good practice to have plenty of ventilation and to wear a respirator approved for use with the specific solvent. Also beware of solvent flammability. The first solvent to try is mineral spirits, commonly sold as paint thinner. If mineral spirits is unsuccessful, VM&P naphtha would be the next solvent to test. These two solvents will remove waxes, so do not use them on pieces with wax finishes unless their removal is the desired result. Other solvents may be successful cleaning agents, but they are also stronger and able to remove certain finishes. Therefore, if mineral spirits and VM&P naphtha are unsuccessful, the cleaning problem should be referred to a conservator.

Solvent cleaning proceeds much the same way as surfactant cleaning - an inconspicuous area should be tested with solvent on a swab for effectiveness and safety to the piece. Test all areas that appear to be different. If cleaning can proceed, lightly moisten a cotton lint-free pad, such as a lithographer's pad, or soft cotton cloth with the appropriate solvent. Follow with a clean, dry cloth. Since all the solvent will evaporate, it is unnecessary to rinse the cleaned area. Remember, if the surface is deteriorated, cleaning should be referred to a conservator.

Furniture Polishing

Do not apply polish to furniture and other collection objects. Oil polishes are of two types, those that dry chemically and are responsible for blackening of the surfaces of objects on which they are used, and those that do not dry, remaining oily and entrapping dust. Concurrently, as drying oils oxidize, they become very difficult to remove. Additionally, many polishes contain silicones and other additives than can cause future finish adhesion problems. Manufacturers are not required to disclose the contents of their products, so there is no way to judge their long-term effect on collection objects. Finally, contrary to advertising claims, these proprietary surface applications do very little to protect surfaces and prevent deterioration. They do not prevent dryness or "nourish" the wood. The temporary improvement in appearance is not worth the risk of potential damage. For these reasons, furniture polishes should not be used on collection items.

Paste wax can provide some degree of protection from water damage for pieces that are in use. Even so, aesthetic enhancement is the major reason to apply waxes to collection items. Properly applied, paste waxes can raise sightly the gloss of the finish, even finish irregularities somewhat and increase the saturation and depth of color of the wood. Unlike oils, they are removable in the future.

If waxing is chosen as an option, use only high quality paste wax such as Butcher's, Minwax, or Renaissance. Do not use oil/wax mixtures. Renaissance wax is very hard and difficult to buff out, requiring a lot of pressure, so it is best to apply one of the other brands to delicate furniture. However, it may be appropriate for iron tools. Reapply wax no more often than every 1-10 years. Generally, between applications, buffing with a soft cloth will restore the luster.

Polishing Metals

Polishing of brass and silver objects, even with the mildest of agents, removes some of the surface metal. After repeated polishings, surface decorations and details can be lost and plated surfaces removed to the base metal. If the polish is not removed completely, residues can act as sites for corrosion of the metal.

Polishing of metals does not enhance their preservation. If metal items are to be polished (this is not a requirement, but a choice), it would be advisable to establish a program of thorough polishing, with proper removal of polish residues, followed by a removable protective coating. Depending upon the specific atmospheric conditions, repolishing and recoating may not be necessary for 20-50 years or longer. See the following Metals section for specific polishing and coating guidelines.

Framed Objects

Framed looking glasses, prints and textiles should not be displayed on exterior walls. These walls are subject to greater temperature fluctuations than interior walls. Additionally, in the winter they are colder than interior walls and can cause condensation of moisture on their surfaces and on the objects touching them, which can lead to mildew growth and object distortion. If possible, framed objects should be removed from exterior walls. If this is not possible, use spacer blocks on the back of the frame to hold it away from the wall and to allow at least a 2" air space behind it for smaller items and 4" or more for larger objects. It is important also to support framed items from two points on the backs of the frames, ideally with D-hooks, from two points on the wall. In this manner, if one support point fails, the second will prevent the frame from falling.

Many paper and textile objects are in acidic mats and backing boards or are not matted at all, pressing the paper or textile against the glass. These items should be properly framed with acid-free materials.

Frames and framed objects should be stored vertically. Shelving units can be utilized for multi-level storage. Large acid-free cardboard boxes can also be used to hold framed objects. Pad the bottoms of the shelves or boxes with several layers of 1/8" polyethylene foam. Use cardboard separators (acid-free is preferred) between each frame to prevent abrasion damage. Place a dust cover over each box or over the entire shelving unit.

Paintings

By their very nature, many paintings are exhibited in the worst possible locations in a room. Many are on exterior walls and thus are subjected to environmental extremes greater than the rest of the room. Others are located on fireplace breasts, with similarly poor environmental conditions. As a result, it is common to find cracked, cupped and cleaving paint. Especially when in this condition, painted surfaces are subject to damage during routine dusting and cleaning. If harsh cleaning agents are used, the varnish and even the paint can be disrupted and damaged. Painting cleaning procedures should consist only of gentle brushing with a soft natural bristle brush that has been used only for this purpose. Do not clean painting surfaces with any other method. Even this procedure may be too harsh for severely damaged surfaces. A painting conservator can be contracted to evaluate the condition and needs of paintings in the collection.

Display paintings on interior walls whenever possible. If display on exterior walls is required, use spacer blocks on the rear of the frame that hold the painting at least 4 inches away from the wall top and bottom, and provide for the free flow of air behind the painting. If the painting is oversized, a greater amount of air space may be required.

Paintings in storage should be stored on padded shelving units or racks as described for framed objects.

Paper/Photographs

Primary preservation threats for paper and photographs are high light levels, mold and mildew growth caused by RH levels that are too high, chemical damage caused by their own natural degradation or their association with acidic materials, and physical damage.

Generally, light levels on most paper/photographs should not exceed 50 lux. This can be difficult to achieve, and in many instances, a level of 150 will have to be accepted. Remove very light-sensitive paper objects to dark storage unless levels of 50 lux can be provided. A paper conservator can assist in identifying these items. Regardless of their sensitivity to light, it is best not to keep paper on long-term display. Rotate exhibited collections with those in storage.

Mold and mildew growth can be controlled only by controlling the relative humidity utilizing suggestions presented earlier in this report. Be aware that isolated locations may have RH conditions that allow growth even though the remainder of the building or even the room do not have problems. These areas typically are exterior walls, floors, and locations with minimal air circulation. Move sensitive objects away from these locations.

Wooden cases used for exhibition or storage of paper-based collections pose preservation problems. All interior wooden surfaces should be sealed with a minimum of three coats of white pigmented shellac (painted) or three coats of unpigmented dewaxed [dissolved in denatured alcohol from flakes] shellac (transparent finish). Allow one to two weeks drying time for the solvent to adequately evaporate. Also acceptable are three coats of polyurethane varnish, but these require a drying time of at least a month to release trapped solvents in them. Coating application does not prevent off-gassing of harmful components, but slows it to a level that is probably safe for most materials.

As an additional precaution, line the bottoms/shelves of the cases with acid-free mat board to absorb acidic vapors that may off-gas from the wood (unbuffered if silk or wool will contact it; otherwise buffered will absorb more acid). On a regular basis, replace the mat board once it loses its acid-free status, probably every 5-10 years for unbuffered and 10-50 years for buffered, depending upon the specific environment inside each case. Be cautious about using modern fabrics or other materials inside cases, as these themselves can be acidic and damage collections. If possible, test the acidity of fabrics before using them (the conservation suppliers have test materials/supplies). It is possible to use acid-free mat board as the visible case bottom without any covering. Acid-free mat board is available in colors to provide more variety in designing exhibits.

If wooden collection furniture is used for display or storage, the application of coatings to seal the wood is not recommended, as this alters the furniture in an irreversible way. Ideally, paper and photographs should not be stored in wooden objects, including in drawers. If this must be done, line the bottom of shelves or drawers with buffered acid-free mat board. If possible, line the backs of drawers and other enclosures with buffered acid-free mat board as well. Do not attach the mat board to the wood, but allow it to free-stand. Additional protection can be provided to paper and photographs if they are first placed in acid-free boxes and the boxes are then be stored in the collection furniture.

Many types of paper produced from the 19th century to date are made of ground wood pulp. Depending upon the individual processing utilized , these types of paper have the likelihood of deteriorating due to their own internal chemical instability. Factors in the environment can accelerate these natural processes. Perhaps the most notorious example is newsprint. Generally, the content of newspapers is more important than the actual piece of paper. It is possible that many newspapers have already been placed on microfilm or on other more permanent media, such as CDís. For these papers, the most effective preservation effort may be to obtain a copy and dispose of the originals. The institution can microfilm or digitize those for which copies do not already exist. Placing important newspapers and other paper objects made of poor quality paper in acid-free boxes is a great way to prolong what is eventually a losing battle.

Proper matting and framing is the suggested technique for preventing physical damage to paper-based objects on display. See the previous section of this report.

A question may arise over whether it is better to exhibit original paper objects or to make copies and exhibit the copies. One concern is about the desirability of showing copies versus the original. Another is over the amount of potential damage that could occur from a photocopying process versus damage from exhibition. In general, the safest method is to make a photocopy, place the original in an acid-free folder in dark storage and exhibit the copy. If a digital image of the object can be created in the duplication process (such as on a hard drive, floppy or CD), additional copies can made as needed in the future without disturbing the original. While exhibiting copies of works of art on paper may not be acceptable, copies of printed and other mass-distribution objects may not be easily detectible from the originals, and may be a preferred preservation technique.

File cabinets may be used for the storage of photographic prints and paper artifacts to prevent physical damage. This type of storage is acceptable provided that the file cabinets are older, having already allowed the paint to off-gas fully, or are new with powder-coat paint. Use acid-free folders in the drawers. Do not crowd objects in each folder, and ideally separate each with acid-free paper. Most plain copy paper nowadays is acid-free, so the cost is minimal. Check with the manufacturer of your paper. Flat ("map") files work well for oversized objects. Alternatively, if they will not be accessed frequently, acid-free tubes can be used for individual oversized paper objects.

Sort through photographic negatives and identify those that are on nitrate film. Have these duplicated onto safety film and discard the nitrate film. It can self-combust and represents a severe fire risk to the collections and the building.

Place individual negatives into mylar or polyethylene sleeves or sheets, which will allow them to be examined in their protective enclosures. Alternatively, they can be placed in acid-free paper envelopes or sleeves. The sleeves and sheets can be stored in acid-free folders in file cabinets or in archival boxes on shelving.

Books

Books have many of the same needs as paper and photographs. The preceding preservation suggestions apply for books as well.

Many books have a preservation concern with their bindings. Leather degrades as a natural consequence of aging. More recent processing techniques (late-18th century to date) can leave chemicals in the leather that hasten deterioration. Exposure to light, poor environmental conditions and handling exacerbate the problem. While many leather treatments claim to improve the problem, research has shown that leather in an advanced state of deterioration can be stabilized only by a conservator and can not be returned to a pre-deterioration state. This type of deterioration is permanent and irreversible. Books with serious leather problems must be referred to a book conservator for evaluation.

Books always present a dilemma with preservation and use. This assessor's perspective is that the institution needs to decide if the book is of artifactual importance or is strictly of informational importance. If the book is important as an artifact (generally, unique or rare), its use should be limited. It can be placed in a special collection such as a "rare book" collection and its use strictly limited to the staff and selected researchers. Such books also can be duplicated so the information is widely available without the need to handle the original.

Duplication methods include photocopying, microfilming and digitizing (either scanning or photography). Make at least two copies if the chosen duplication method is not digital. Keep one of the copies in protected storage for use as a master when the circulation copy becomes unusable. In this manner, the original does not have to be subjected to duplication a second time. While duplication processes require short-term exposure to high light levels, the duration is so brief that no discernable deterioration occurs. Damage from handling during duplication probably is a higher deterioration risk.

Once copies have been made of "rare" books, the originals can be stored in acid-free boxes on metal shelves. This will protect them from light, dust, dirt and to some degree, short-term environmental fluctuations.

Scrap books and photo albums present similar preservation challenges to rare books, except that the original materials usually are of poor quality and are subject to accelerated deterioration. In addition, scrap books are composites of different objects and materials, often held to poor quality paper with glue, which itself can cause deterioration. Preservation options for scrap books are individualized depending upon the specific book, but in general, they can be thought of as very difficult to preserve long-term. Specific suggestions can be obtained from examination by a paper conservator.

As a general preservation suggestion, duplication may be the best alternative for scrapbooks and photo albums. This assessor likes the option of digital photography. Digital cameras capture not only the informational content of the scrap books and albums, but also the appearance in color. Once the necessary equipment has been purchased, operating costs are extremely low, since there is no film or processing. Storage can be on hard drives, floppy diskettes, Zip drives, tape or CD. As a very rough example, a medium resolution digital photo uses about 100 KB of storage space, so roughly 15 photos would fit on a high density floppy disk.

For Museum purposes, storage on a CD seems the most appropriate alternative, partially because the other magnetic media have questionable life spans. Prices for a recordable CD drive begin around $200 and CD's cost as little as $1 each for a recordable CD. Do not use re-recordable CDís for archival purposes, since their life span is significantly shorter. Each CD stores 650 MB, which is enough space for about 6,500 medium resolution photos. Using a standard CD, an entire scrap book or album could be placed in digital form for the cost of $1 (exclusive of initial equipment and labor). In fact, multiple scrap books or albums could be placed on a single CD, but this may be more confusing than each on its own CD. Circulation copies of the CD's can be self-made, holding the original in the files as the master. Each of these copies would be identical in quality to the original.

In a similar manner, oral histories on magnetic tape could be converted to digital format and stored on CD's. Alternatively, they could be transcribed via voice recognition software. These software packages are less than $100 and can be trained to have very good recognition of individual voices. After computer transcription, there would be some correction and cleaning up required. Magnetic tape will not survive long-term, and the histories will be lost if they are not converted in some manner. Videotapes also share a similar preservation need. Digitizing them and placing them on a CD may solve this problem as well.

Textiles

Display of textiles presents difficult choices. If they are shown in period uses on beds and furniture, they are subject to excessive light, with resultant fading and weakening, and accumulation of dust and dirt. If they are stored away, they will be better preserved but will not be accessible to visitors. Where possible, rotate textiles with others in collection storage or use reproductions for open display.

Dust will accumulate in open display and cannot be prevented. The only viable method of prevention, covering the textiles daily when they are not on view, runs the risk of damage from abrasion. However, textiles and other sensitive materials can be protected with light-weight polyethylene or cotton dust covers during the winter season when the institution is closed for visitation. Year-round, try to remove as much dust from the air as possible by routine dusting of other objects in the rooms and use of dust filtration systems. It is not possible to dust the textiles. Periodically, it may be necessary to clean them. This may be possible by proper low-suction vacuuming through a fiberglass screen or may require more extreme measures. A textile conservator should be consulted for cleaning advice.

Keep pens and water-soluble ink away from textiles. If the objects were wetted during a disaster or accident, the ink on signs or labels could cause irreversible stains. Textiles displayed on beds or mannequins may be directly on top of materials that are not the most stable or chemically neutral. Therefore, a layer of acid-free tissue beneath them is suggested to act as a barrier.

Display of uniforms or clothing on mannequins creates a preservation concern. Most mannequins are not designed for long-term display. They are made of materials that are not archival, and the materials break down with time and can damage clothing on them. If commercial mannequins are utilized, line all surfaces that touch the clothing with several layers of acid-free tissue paper. Change the tissue paper periodically as it becomes acidic. The frequency depends upon a number of factors, so measuring the pH is the most reliable method. As a rough rule of thumb, the paper should be changed every 10 years, although this interval should be shortened or lengthened as required for each specific situation. It is likely that different mannequins will present varying preservation risks, so the same time interval may not work for all of them.

Uniforms and clothing in storage generally are displayed on hanging racks. Dust covers should be placed over the entire racks, or over individual items. For most situations, light weight polyethylene dust covers are suggested, such as those used by dry cleaners. They are available from archival/conservation suppliers. Replace all existing covers of unknown composition. Do not seal the bags at their bottoms. While this can prevent some dust from entering the bag, it also can encourage accumulation of vapors inside the bag from volitization of the components of the clothing. If the collection has only a few clothing items, they can be stored in large acid-free boxes with proper padding using acid-free tissue. Additionally, weakened clothing/costumes may not be able to support their own weight on hangers. These items can be stored in acid-free boxes as well.

Clothing needs to be hung on padded hangers that are archivally stable. Archivally acceptable padded hangers can be purchased from archival/conservation suppliers, or can be made by Museum staff or volunteers. A good resource for suggestions on making hangers and other textile/clothing care issues is the Textile Conservation Center of the Museum of American Textile History in Lowell, MA (978-441-1198).

Insect infestation of clothing, particularly that which is made of wool, is a major preservation concern. The best defense is vigilance. Inspect the clothing thoroughly every 3 months. This can be done quickly without removing the dust covers, provided that transparent archivally stable covers are used. Every garment needs to be individually inspected. Write this into the cyclical maintenance plan.

Smaller textiles can be stored in acid-free boxes. Separate between each with acid-free tissue and do not crowd the boxes. Use buffered tissue for cottons and linens (provides greater useful life) and unbuffered for wools and silks (which can be damaged by the buffering agent). If in doubt about the nature of an object, use unbuffered tissue. Open the boxes on a regular basis (perhaps once a year) and inspect them for infestation problems. Write this into the cyclical maintenance plan.

Generally, folding textiles and clothing is not ideal for long-term storage. Often, the folds become set and the region becomes brittle, making unfolding very difficult. However, if folding is necessary, pad the folds with crumpled-up acid-free tissue. Do not crowd boxes or stack many objects on top of one another.

Large flat textiles such as quilts, coverlets, flags and rugs should be stored horizontally on a rolled rack. Carpet tubes (often available for free from carpet installers) covered with polyethylene or Mylar, followed by acid-free tissue, will work well for support. Place a dust cover of mylar, polyethylene or unbleached fine-weave muslin over the rolled textiles.

Furniture and Wooden Objects

Rising relative humidity causes an increase in moisture content of wood and expansion across the grain, with a corresponding shrinkage when the relative humidity falls. Rising temperature causes shrinkage of wood and falling temperature, expansion. Within the environmental range encountered in Museums and historic houses, the effect of relative humidity changes is far greater than that of temperature. For conceptual purposes, a relative humidity change of 10% is roughly equivalent to a temperature change of 60 degrees F. Generally, temperature and relative humidity are inversely related. If the temperature increases, the relative humidity falls and vice versa.

In a totally unrestrained board that is rather narrow, the effect of expansion and contraction caused by fluctuating relative humidity and temperature may be minor. However, if restraint in any form is present, such as attachment to other boards, or if the board is wide, cracking, splitting, warpage, and veneer delamination can result. Restraint in historic objects is greatest in cross-grain construction - when one wooden member is attached to another and the grain directions are perpendicular to one another.

Light bleaches the colorants in wood, and cracks and crazes finishes and paints. This damage is permanent and irreversible. A good example is the piano in the Parlor of the Horatio Colony House Museum. Light can contribute to surface cracking of wood by heating the surface but not the interior. Light levels should not exceed 150 lux on furniture.

Do not apply polish to furniture and other collection objects. Oil polishes are of two types, those that dry chemically and are responsible for blackening of the surfaces of objects on which they are used, and those that do not dry, remaining oily and entrapping dust. Concurrently, as drying oils oxidize, they become very difficult to remove. Additionally, many polishes contain silicones and other additives than can cause future finish adhesion problems. Manufacturers are not required to disclose the contents of their products, so there is no way to judge their long-term effect on collection objects. Finally, contrary to advertising claims, these proprietary surface applications do very little to protect surfaces and prevent deterioration. They do not prevent dryness or "nourish" the wood. The temporary improvement in appearance is not worth the risk of potential damage. For these reasons, furniture polishes should not be used on collection items.

Paste wax can provide some degree of protection from water damage for pieces that are in use. Even so, aesthetic enhancement is the major reason to apply waxes to collection items. Properly applied, paste waxes can raise sightly the gloss of the finish, even finish irregularities somewhat and increase the saturation and depth of color of the wood. Unlike oils, they are removable in the future.

If waxing is chosen as an option, use only high quality paste wax such as Butcher's, Minwax, or Renaissance. Do not use oil/wax mixtures. Renaissance wax is very hard and difficult to buff out, requiring a lot of pressure, so it is best to apply one of the other brands to delicate furniture. However, it may be appropriate for iron tools. Reapply wax no more often than every 1-10 years. Generally, between applications, buffing with a soft cloth will restore the luster.

If there are powder post beetle or furniture beetle holes (round, about the size of a pin head) in wooden objects which appear fairly fresh and light colored, infestation may be active. Fill existing holes with brown pigmented wax (for darker objects) or natural colored wax (for light objects) and look for the appearance of new holes. If they are found, immediately isolate the object and have it fumigated with Vikane (sulfuryl fluoride) in a dosage that is 10 times that recommended for dry wood termites.

For a more detailed discussion of the preservation of furniture and wooden objects, please refer to Keeping It All Together by assessor Marc Williams, as well as Appendix 2 of this report.

Metals

The primary preservation concern for metals is the chemical changes that can occur to their surfaces. A number of factors cause these changes. While metals are themselves not significantly responsive dimensionally to the relative humidity and temperature of their Museum environments, unlike wood, paper and textiles, extremes of environment can accelerate other processes. High RH promotes corrosion (rusting for iron). High temperature increases oxidation or speeds up corrosion when the RH is sufficiently high. Thus, RH levels below 50% at moderate temperatures are preferred. In fact, metals will survive quite well at very low RH levels with no negative effects.

Metals are corroded by chemicals in their environments. Three primary sources are responsible. The first is salts and oils on human hands. Use white cotton gloves when handling metals to prevent corrosion from fingerprints. The second source is pollutants in the air. This is much more difficult to control without sophisticated air filtering systems. Very rare or valuable objects may require custom-designed cases if local levels of pollutants are high. The third source is other harmful materials in the presence of metals. Several examples will illustrate the concept. Wood naturally off-gasses components that may corrode metals if the concentrations are sufficiently high, such as inside cases. Most dramatic is the formation of lead acetate, which turns lead collection objects white in color. Another example is the effect of rubbers on silver objects. Volatized sulphur will tarnish silver and turn it black.

Polishing of brass and silver objects, even with the mildest of agents, removes some of the surface metal. After repeated polishings, surface decorations and details can be lost and plated surfaces removed to the base metal. If the polish is not removed completely, residues can act as sites for corrosion of the metal.

Polishing of metals does not enhance their preservation. If metal items are to be polished (this is not a requirement, but a choice), it would be advisable to establish a program of thorough polishing, with proper removal of polish residues, followed by a removable protective coating. Depending upon the specific atmospheric conditions, repolishing and recoating may not be necessary for 20-50 years or longer.

The safest polishing is done with a paste of precipitated chalk in distilled water, followed by rinsing with distilled water. Use a soft cotton pad or Q-tip to apply the polish paste with gentle rubbing. Coating can be done in-house by staff, but use of a professional conservator is recommended due to the importance of applying an even coat and due to solvent safety concerns. Coatings to be considered are Acryloid B-48N (Rohm & Haas) and Agateen lacquer (Agate Lacquer Co.). Polishing and coating would not have to occur all at once, but could be undertaken over a period of several years.

Ferrous metals present an especially difficult preservation problem. Relative humidity levels above 50% promote active rusting of their surfaces. Protective coatings will slow this process initially, but eventually rusting will continue under the coating. Current conservation knowledge does not offer any satisfactory solutions to this problem, other than removing the items from the hostile environments and placing them into a lower RH environment. On a test basis, paste wax can be applied to iron objects. The wax may provide some additional protection from environmental extremes. If it is effective, apply it to other iron collections items. If not, discontinue its use. Cleaning procedures prior to wax application, if required, depend upon the needs of the specific object, so a conservatorís advice should be obtained.

Glass and Ceramics

Most glass and ceramics and not affected by the relative humidity and temperature levels found in most Museums. Therefore, they can be exhibited and stored in almost any location. Most that have a continuous glaze also are not significantly affected by dust and dirt (crazed surfaces can collect dirt in the cracks), nor are insects a problem.

However, glass and ceramics are highly susceptible to breakage, and care must be given to protecting them from falling in both exhibition and storage. The use of cabinets and cases can assist with protection. Installation of restraints at shelf edges can prevent objects from vibrating or being knocked off of the shelves. Earthquake wax (available from conservation suppliers), developed to attach objects to their supports in a reversible, non-destructive way, can also hold breakable objects in place.

Flowers

The presence of cut flowers and live plants in the collection areas leads to several potential problems, the most severe of which is the introduction of insects to the collections. These can include clothes moths, carpet beetles and furniture or powder post beetles. Unless the plants are fumigated, this risk cannot be eliminated, as many of these insects are quite small and cannot be seen easily upon inspection of the plants, or the plants may contain insect eggs. Other risks from plants include abrasion caused by their containers, increased levels of dust, dirt and pollen, and damage due to accidents or spills. The safest alternatives are to exclude flowers and plants from the collections or to use silk flowers.

Food and Drinks

Food serves to attract insects and rodents, which can damage collection objects. Additionally, food and drink can itself stain surfaces or even dissolve finishes and distort paper. Food and drink should not be allowed in the collection areas.

Conservators

When the Museum is at a point that treatment of the collections becomes a priority, the overriding principle should be preservation of original surfaces. For example, far too often painted surfaces are stripped and repainted and early furniture finishes are removed, resulting in surfaces that are reproductions, not originals. Thus, the visitor sees a modern interpretation of an historic object, rather than the maker's intent. A worn and imperfect, but original, surface speaks so much more eloquently about history.

Collection items should be treated only by skilled conservators who possess the knowledge, materials and skills to do a proper treatment. Do not use volunteers, board members or restorers. A Condition Report and Proposed Treatment should be provided prior to treatment and a Treatment Report submitted after treatment, complete with photographs. These should be kept in the curatorial files. The American Institute for Conservation (1400 16th Street, NW, Washington, DC 20036, 202-232-6636) has available a brochure "Guidelines for Selecting a Conservator" which may help in this process.

 

Further Collections Care Information

A good resource for questions on conservation issues, including routine care and maintenance, is the Smithsonian Center for Materials Research and Education. Located at the Museum Support Center, Suitland, Maryland, they can be reached at 301-238-3700.

Other sources of information include "Conservation Notes" and "Technical Bulletins" published by the Canadian Conservation Institute (1030 Innes Road, Ottawa, Ontario, Canada K1A 0M8, 613-998-3721). These are available free of charge and cover many specific areas of care of collections. Also of assistance are the technical information services of the American Association of Museums [AAM] (Washington, DC , 202-289-1818) and the American Association of State and Local History [AASLH] (Nashville, TN, 615-255-2971).

A notebook of technical leaflets entitled "Preservation of Library and Archival Materials." is available from the Northeast Document Conservation Center (978-470-1010, $40 postpaid) as a resource for paper preservation needs.

A final resource for archival and paper questions is the Preservation Help Line, funded by Gaylord, the archival/conservation supply company. Staffed by an independent conservation professional, it can provide custom answers to preservation questions at 800-428-3631. Listed hours are Thursday and Friday from 9-5 EST, but it is best to call and verify current hours. 

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