CRITERIA FOR TREATMENT: REVERSIBILITY
4 REVERSIBILITY, INTERNAL CONSOLIDATION, AND RE-TREATABILITY”
Even if an internal consolidant is easily soluble, it is unlikely that much can ever be removed, particularly since objects that need consolidation are by definition so weak that repeated applications of solvent may cause damage. Even if solvent vapors are used, the deeper the impregnant has penetrated, the less likely removal is.5 Even a minor treatment like injecting warm gelatin under loose flakes of paint is not reversible, as there is no physical access to the gelatin lodged between the layers of paint after the paint is laid down. If internal consolidation with easily soluble materials will not be reversible in the future, then what criteria should be applied for the choice of material?
Impregnation is one example of a sometimes necessary but irreversible treatment. As with any treatment, impregnation must satisfy the requirements of aesthetic appropriateness and physical and chemical compatibility, but if it is irreversible upon completion of the treatment, reversibility during the course of the treatment must also be considered. Can drips or pools of impregnant be removed from the surface of the piece before the material sets? What can be done in the course of treatment to adjust the gloss of the surface? How much control is there over the appearance of the piece? What happens if the treatment does not proceed exactly as the conservator had expected?
An equally important question is: what will happen when the piece needs treatment again, particularly if the problem that necessitated the treatment recurs? Can the same treatment be repeated? Can a different material be used with the first one still in place? What can be done with written condition and treatment records to make it more likely that a future conservator can find out what was done? The undertaking of an admittedly irreversible treatment does not absolve the conservator of responsibility for the future of the object, but increases the importance of a factor we might call, for want of a more elegant term, “re-treatability.” The notion of re-treatability is one that is often more helpful in evaluating treatments than the idea of reversibility itself. This is particularly true in the impregnation of badly deteriorated materials, since the treatment strengthens what is left of the object but may not prevent further deterioration of original material, and re-treatment may not be far in the future.