Alaskan Ten Agents of Deterioration

Pollutants that threaten collections take many forms. Sometimes pollutants are damaging substances that are directly touching objects. Sometimes they accumulate on objects as dust. Other times they are invisible, such as volatile organic compounds from acidic materials. Being aware of pollutants can lead to better collections management.

Institutional policies and procedures are important defenses against pollutants. Keeping food and beverages away from collections can prevent damage from spills and pests (figure 1).

Dust is another pollutant that can be controlled with good institutional practices. Dust is abrasive, hygroscopic (attracts water, which can promote corrosion), is nutritive to biological growth such as mold, and supports colonies of bacteria that leave acidic and sticky waste products on collections. Figures 2 and 3 show extreme dust build-up on objects. An article describing the issue of dust in exhibits is attached here:

Good museum practice calls for gloves to be worn when handling collections. Oils and moisture from the skin can damage or stain many materials. Metals in particular are vulnerable to touching. Figure 4 shows corrosion resulting from handling silver without gloves. The disfiguring corrosion can be removed by polishing, but each time an item is polished, a little bit of surface is lost. Objects with gold wash surfaces, planishing marks, signatures, and other delicate features are damaged by excessive polishing.

Sometimes pollutants from poor but well-intended collections care cause damage to artifacts. Acidic papers and cardboards release acids that tend to cause yellowing (figure 5). Many plastics are not stable for long-term storage. Polyester (such as Mylar) and polyethylene (used in many plastic bags and foams appropriate for museum use) are stable plastics. PVC (polyvinyl chloride) and urethane are examples of plastics that harm collections. Food grade materials, for example, are rarely meant to stand the test of time. Flexible plastics usually contain chemicals called plasticizers which tend to break down and ooze over time or react with object surfaces (figure 6). Soft urethane foam is appropriate for shipping purposes if there is a barrier between the foam and the object, but over many years this kind of foam gets brittle, crumby, and sticky (figure 7).

Leather dressings were once widely applied in an effort to maintain leather in a supple state. Museums experimented with perfecting the best oils and lubricants to apply to leather, but by the 1980s realized these dressings were causing more harm than good. Examples of the reasons the Alaska State Museum does not use leather dressings are given in this article:

Commercial polishes used on metals sometimes leave residues, and commonly contain harsh ammonia. Ammonia is known to weaken copper alloys through “corrosion stress cracking.” Metals with texture or complex decoration sometimes have residues of polish left behind as telltale white deposits with a greenish tinge (figure 8).

Tapes and adhesives cause significant damage to collections, especially paper materials. There is no such thing as archival tape. Over time, the sticky part of a tape will migrate into a material, frequently causing staining and weaking in that location. The use of sticky substances directly on an object should always be avoided. Poster putty is another example (figure 9).

Metals are particularly vulnerable to pollutants. A common museum method for testing storage and exhibit supplies is called the “Oddy test” and involves exposing the test material to polished pieces of lead, copper, and silver under controlled conditions. Lead, for example, corrodes with white crusts when exposed to certain pollutants (figure 10).