Although treatment of an object may sometimes be necessary, treatment alone is not sufficient to preserve collections for future. Objects inevitably deteriorate, but our objective as preservers of material culture is to slow the rate of deterioration as far as possible. Preventive conservation efforts aim to reduce damage and deterioration to collections by improving their environment. Measures include areas such as: Controlling temperature, relative humidity and pollutants; Archival housing; Loan documentation and packing for transport; Integrated Pest Management; Cleaning and housekeeping; Emergency preparedness and response; Handling procedures; Hazardous materials.
Relative Humidity, Temperature and Pollutants
All materials respond to their immediate environment. Very high relative humidity is conducive to mold growth. Fluctuating relative humidity causes organic materials like wood, ivory, and paper to cycles of expansion and contraction leading to cracks, broken paint, and warping. Particulate pollutants like dust, sand grains and soot are carried into the museum from urban and agricultural environments. Sharp grains like sand lead to abrasion of object surfaces. Soot is grimy and acidic leading to discoloration, embrittlement of organic materials and corrosion of metals.
Preventing damage to objects is more cost-effective than allowing the damage to happen and then treating it.
Acidic gaseous pollutants from urban traffic have caused this gold alloy figurine from Peru (FMNH 2414) to tarnish everywhere except under the varnish associated with the catalog number on its chest.
Some materials may be inherently unstable and require a specific environment to reduce further degradation. For example, soda-lime-silica glass that was not made with the correct proportion of silica, soda flux and lime stabilizer will degrade with high and fluctuating relative humidity (glass hydration disease). This glass will continue to degrade unless held at a very constant relative humidity of 40-42%.
The white crystals on these beads from are flux and stabilizer ions from the glass that leached out with fluctuating humidity and then combined with carbon dioxide in the air to form the white carbonate minerals.
For long term preservation, it is critical that object housing provides physical support to the object and that the housing materials are archival (chemically stable materials that will not cause harm to the object). Conservation staff study manufacturer’s data and conduct artificial aging and chemical tests of materials to select materials for storage housing and display mounts that are archival. The object structure and condition determines the support needed to prevent distortion and breakage over time.
Loan Documentation and Packing for Transport
All objects going on loan to other institutions are carefully examined to make sure they can safely travel and are packed to reduce the vibration and shock inherent in vehicular and air transport.
IPM (Integrated Pest Management)
Protecting the collections from damaging pests is a museum-wide endeavor. The Museum Pest Committee, working with contract pest specialists and entomologists, includes members from each division of the museum, including Facilities, Housekeeping, Collections, Exhibits, Special Events, Administration and Institutional Advancement. The Committee tracks pest activity in the museum and immediate grounds, advises on and coordinates pest mitigation and response activities. Given that many collections within the Department of Anthropology are highly attractive to insect, rodent and mold pests, Anthropology staff are highly sensitized to the danger of a pest infestation.
Cleaning and Housekeeping
Dust and debris in collection storage and workrooms provide attractive environments for damaging pests. Dust falling on objects is often difficult to remove without disrupting the fine structure of materials like feathers and matte paint. Access to storage is limited to reduce the build-up and movement of dust and dirt. Workrooms are regularly cleaned by housekeeping staff. Anthropology staff conduct an annual in-depth cleaning of all storerooms to remove any clutter that may have accumulated and reduce the dust load in storage.
Emergency/Disaster Mitigation and Response
Disaster Planning includes identifying potential risks to the collections, mitigating those risks through improvements to the building, the object storage and exhibit furniture, and procedures. Disasters may be caused by natural events like flooding, tornados, earthquakes, and by man-made situations like leaking pipes, breakage of vitrines and fire. The Anthropology Department developed and maintains a policy and procedures for responding to disasters. We work with local agencies like the Chicago Emergency Response Office, the fire, Police, and other Chicago cultural institutions, to identify resources available.
When accidents do occur, museum staff respond immediately to reduce damage to collections.
Objects can suffer breakage and staining through inappropriate handling. All department staff, researchers, interns and volunteers are given training in lifting, supporting and transporting objects. Gloves are worn to prevent the deposition of hand oils, perspiration and soil. Padded carts with pneumatic wheels are used to move objects. Safe ways to lift different object types are reviewed.
Hazardous materials pose a risk for staff working with collections. Some hazards may be inherent to the objects themselves, for example pigments made of arsenic or mercury minerals. In other cases, toxins may have been applied to an object in early efforts to reduce insect damage. Objects are tested for toxins [photos sampling, testing] and housed and labeled if positive [photo labeled housing]. Procedures have been developed with the Field Museum health and safety officer and public health advisors to protect staff and researchers who handle collections. Gloves, lab coats and sometimes masks are worn to protect staff.