Cultural property storage
[1] The basic idea of climate control is to keep the temperature and relative humidity at a steady rate so as to avoid expansion and contraction of materials, which can cause serious damage.
[6] As with temperature control, the main goal of the control of relative humidity to is avoid major fluctuations which can cause physical damage to objects, with long term seasonal changes causing greater damage than short term changes.
[7] Hygroscopic materials such as wood, textiles, and bone, are especially sensitive to changes in humidity, as they swell and shrink according to the environment, which will cause deterioration over time.
[4] A very low relative humidity, of about 35% or lower, can cause embrittlement of paper and adhesives, as well as cracking and warping of wood and ivory.
[7] An ongoing monitoring system is essential to the preventive care of objects in collections storage, as it helps to identify any problems, evaluate the effectiveness of corrective measures, and document the effect of extraordinary events such as water leaks, long periods of drought, or heavy rains.
[4] Hygrothermographs are a tool that constantly monitors both the temperature and relative humidity, and are fairly reliable if properly calibrated, a task that must be completed at least every three months if not more frequently.
Hygrometers, thermometers, and thermohygrometers are also useful for determining the temperature and relative humidity of a space, but the most reliable tool is a psychrometer.
[1] This type of system allows great variation, as the distance between racks can be adjusted to accommodate large or small frames, and works can be organized to make the most of the space while keeping them in their upright position to avoid damage.
[1] Open steel shelving systems are cost effective, and easily adjusted to accommodate objects of various sizes.
[1] It is also necessary for cabinets to be stabilized by being bolted to the floor or walls, and for shelves to have restraining bars, to avoid tipping, especially in earthquake prone areas.
[1] Dividers can be made to fit in shallow drawers to create individual compartments for small objects like coins, or small individual boxes can be utilized in the same fashion, which allows the entire box to be removed so the object itself is handled less.
[3] Boxes can add an additional layer of microclimate insulation and make moving objects easier.
[3] Polyethylene and polyester are considered archival plastics because they do not offgas harmful chemicals, but they can produce static electricity in a low RH, so they should be avoided around friable objects.
Archival fabrics are typically washed before use to remove sizing chemicals and to soften the material, and are never dyed.
[3] Many museums are beginning to opt for open storage spaces that allow visitors to see more of the collections and behind the scenes activities.
