Just Because You Can Doesn’t Mean You Should: The Case of Reversibility
One of the key rules in the conservation of artifacts is that the work must be reversible. However just because something can be reversed does not mean it should be reversed or that the reversing process could actually damage the artifact. This becomes a judgment call for a conservator to determine if the process of reversing a past conservation effort will damage the artifact more than leaving it with its current treatment.
Resins and polymers are often used in the conservation of organic material to add structural integrity to the internal system of weakened artifacts. The question becomes can a resin or polymer be reversed without the internal system of an artifact collapsing on itself. This collapse may actually be part of the re-treatment process because the removal of the old resin or polymer must take place before the artifact is treated with the new resin or polymer. To understand the treatment process a person must appreciate that often organics such as bone, wood, and even types of paint (egg-temper base) will have microscopic holes throughout their structure as they deteriorate. As the organics decay the holes widen and the structure becomes weak. Resins or polymers can fill in the holes left from decay adding support. Often during the reversibility of treatments the solvents used can cause damage to an artifact. In some cases, these must first be applied to remove the old resin and polymer buildup so that new conservation methods can be used. One example is related to the treatment of a painting. Gelatin was injected under loose paint but this treatment is really not reversible as the paint would come off once a solvent was applied to remove the gelatin (Appelbaum 1987). In this example, it is clear that the gelatin used by conservators to help stabilize the painting would ultimately damage the painting. This becomes an ethical issue for conservators when considering if reversing a treatment with possible damage to an artifact outweighs the damage of leaving it in its current condition with old methods of stabilization.
Another example is related to the conservation of bone. This has its own issues not only for long-term preservation and for stabilization, but also because bone is used for forensic analysis (Johnson 1994). It is important that the conservator take this into consideration that any resin or polymer used on ancient bone has the potential of changing the results from any chemical analysis used by archaeologists. However, it is possible that the chemical analysis can still be done if the archaeologist is aware of the chemical makeup of the resin or polymer that is used in the conservation or stabilization of ancient bone.
Once a conservation method has been determined and used on an artifact for display, it is also important to remember the display environment can have an effect on the stabilization. In situations where humidity and temperature are not controlled properly, artifacts can retain moisture that can damage or break down the resins adding further damage to the artifacts (Sanford 1975). If an artifact does get wet from humidity and temperature fluctuations, biological growth can occur, adding further decay to an artifact. If this were to happen the artifacts would need to be retreated which might add to further damaging the structure of the item.
Conservators are faced with a tough job when it comes to finding the balance between artifact stabilization and treatment methods versus whether a treatment is truly reversible without further damaging the artifact itself. It might be in the artifacts best interest to not reverse a past treatment and risk the integrity of the structure if the past treatment is still stable. As new technologies become available, old treatments might become obsolete, however new techniques have not stood the test of time yet so their longevity is still questioned.
Appelbaum, Barbara. 1987. “Criteria For Treatment: Reversibility.” Journal of the American Institute for Conservation 26 (2: 1): 65-73.
Johnson, Jessica S. 1994. “Consolidation of Archaeological Bone: A Conservation Prespective.” Journal of Field Archaeology 21 (2).
Sanford, Elizabeth. 1975. “Conservation of Artifacts: A Question of Survival.”