Storage Environments and Furniture

High temperatures are generally bad for collections because they promote physical aging and deterioration. On the other hand, temperatures that are too cold can promote thermal shock, in which a specimen could become brittle and crack or shatter; they can also be uncomfortable for people working in the collections. Widely fluctuating temperatures can cause a variety of kinds of damage to specimens.

Incorrect temperatures also can lead to changes in the crystalline structure of minerals; soften adhesives that are used in fossil preparation, resulting in slumping; and, when combined with high relative humidity can lead to mold growth on specimens, labels, and storage containers. Generally speaking, a steady temperature  of 68-70 degrees Fahrenheit represents the best compromise for good collections care and human comfort. For paleontological collections the National Park Service Museum Handbook recommends temperatures of 59-77 degrees Fahrenheit.

Relative humidity (RH) is closely linked to temperature; warm air holds more moisture than cool air.  For the best storage environment, the goal is to keep RH levels moderate and stable.  That means keeping RH generally close to 50% and attempting to minimize short-term variation to between 45-55% even if broad seasonal trends are hard to avoid.  Large shifts in RH may result in physical damage to specimens; fractures and crumbling can occur as the specimen alternately absorbs or releases moisture, causing swelling or shrinkage.  High RH can also promote oxidation and corrosion of certain minerals, such as iron pyrite.

A variety of different environmental control strategies can be used depending on the situation – at the macro level this includes centralized control of air temperature within a building (with or without active relative humidity control); room level temperature control (e.g., radiators with window mounted a/c units); or entirely passive control based on the buffering effects provided by the building itself (which can be improved by additions such as door and window seals).

Controlling RH at the building or room level can be very expensive, and if not done properly may actually end up causing structural damage to the building. However, RH can sometimes be very effectively, and relatively cheaply controlled by creating a micro-environment around the specimen, using a combination of well-sealed storage cabinets or exhibit cases and buffering materials, such as acid-free tissue, wooden drawers, and silica gel.

Even if you have limited ability to control the environment or your collection buildings or rooms, it is a good idea to know what conditions your specimens are being subjected to, so that you can  anticipate problems and come up with micro-climate level solutions when possible. Monitoring environmental conditions can be done using equipment such as Heating Ventilation and Air Conditioning (HVAC) and/or Building Management Systems (BMS); if you don’t have access to these, reasonably priced electronic data-loggers or recording hygrothermographs are available and can be used very effectively.

The most common and problematic contaminant for fossil collections is the dust and dirt that builds up in storage areas without proper housekeeping. Well-sealed cabinetry greatly reduces this problem, but can create other problems if the materials of the cabinetry (or the storage materials contained inside) off-gas, leading to a build-up of harmful gaseous pollutants. 

Contaminants can also come in the form of chemicals used in the preparation of specimens (e.g., acids or salts not rinsed away after treatment) or materials used in treatment such as adhesives and consolidants. Specimens suffering from pyrite disease emit sulfuric acid, which will contaminate storage materials and damage other specimens nearby. Any specimens suffering from pyrite disease should be isolated from the rest of the collection.

Most fossil specimens are not directly affected by either visible or ultraviolet light, but other mineral components of a collection can change color, change phase, or decompose in response to high light levels. A bigger concern for paleontology collections is the ability of light to affect adhesives used in the preparation or preservation of a specimen, as well as its effect on other collection housing materials. Light damage is cumulative and irreversible. As a result it’s a good idea to limit light exposure if possible.

• Make sure circulating air in the collection is as clean as possible by using filters on your A/C or HVAC system and making sure that they are changed regularly
• Keep windows closed in storage areas
• Keep specimen cabinet doors closed
• Use dust covers on open shelving

Specimen cabinets are probably the most common form of collection storage. The main purpose of a specimen cabinet is to protect the specimens from the harmful effects of dust, light, and insect pests; from theft; and from unnecessary handling. Cabinets can be either stationary or (if the load bearing limits of the flooring and collection building allow) mounted on rails (compactors) to save space. Specialist museum cabinetry is usually made from steel and offers features such as lockable gasketed doors, which form an airtight seal when the cabinet is closed, and a powder-coated paint finish which is resistant to changes in RH and does not off-gas pollutants.

They may have a built-in leveling system, to cope with uneven floors, and raised bases to reduce the risk of flood damage and remove shelter for pests. They are generally made to order by one of a limited number of suppliers, and as a result are relatively expensive. However, they have a lifetime which can be measured in decades and represent a good long-term investment for the well-being of the collection.

The older generation of specimen cabinets was often wooden, and it’s not uncommon for many collections to re-use old wooden drawers in modern steel cabinets. Wood offers some advantages for collection storage, because it responds to changes in RH and can buffer specimens against fluctuations in the environment. However, this can also lead to drawers “sticking” in their tracks in conditions of raised RH; forcing drawers can lead to unnecessary vibration for fragile specimens. Some wood products will off-gas, which could have a negative impact.

Bulk storage racks are particularly useful for housing medium- to large-sized specimens and field jackets that may not fit into a specimen cabinet, or may be too heavy to place in a drawer. As with cabinets, they can be static or mounted on compactors. They can have metal, plywood, or wire mesh decking that can be sealed and padded. Open shelving provides less security and protection than a specimen cabinet. However, polyethylene sheeting can be hung from the top of the rack to provide protection against dust buildup.

The main advantage of open racking is that it makes it easier to handle large, heavy, or unwieldy specimens. For this reason, it is important that the rack is positioned for maximum accessibility; it should be accessible from both sides and there should be sufficient aisle space between racks to allow for a ladder or fork-lift to be brought alongside the shelving.

Heavy duty storage racks, often rated at 2,000 lbs or more per shelf, are commonly used in commercial and industrial settings and can be purchased comparatively cheaply.

Moving the largest specimens, which may weigh hundreds of pounds, may require a pallet jack or fork-lift. To assist with this, the specimens should be placed on pallets, which can be placed at floor level or mounted on storage racks. In placing the pallets, it is important to allow sufficient space to maneuver either a lift or jack.