6 DISCUSSION

MATERIALS USED IN CONSERVATION should be stable over an extended period of time. This does not seem to be the case for the polymer dispersions tested. Discoloration (the formation of conjugated double bonds) occurred in measurable amounts in all samples after a relatively short exposure to aging conditions. Changes in peel strengths related to the aging of films indicate increased difficulty of reversibility in the Rhoplexes and 498 HV. While the precise peel strength desirable would depend on a number of factors not examined here extreme highs and lows were judged to be undesirable. The extremely high peel strength value for HV 360 makes its reversibility a harsh undertaking for a fragile art object. Conversely, reactivated samples with low peel strengths do not have the adhesive strength to keep a fabric securely adhered to another and so threaten delamination. Changes in technique of reactivating the adhesive may be required if it is to be used in the lining procedure.

Of the five adhesives tested, the Plextol B500 appears to be the most resistant to peel strength changes over time. Unfortunately, it also sustained the most discoloration of any of the adhesives. Since the adhesive would be hidden from light in a lining, yellowing may not be a factor under consideration. Accepting a material's negative properties to gain the advantage of its positive properties is a compromise frequently made in conservation. Certainly the discoloration of any of these materials is inevitable and must be considered vis-ll

l3mbined adhesives could be tested to determine if a mixture of two adhesives would yield more favorable properties than either one used alone. Comparison of peel strength vs. sheer strength values would further enhance understanding of these materials. There are many avenues for further study of the use of these materials in the conservation field.