THE PROPERTIES AND LIGHT STABILITY OF SILK ADHERED TO SHEER SILK AND POLYESTER SUPPORT FABRICS WITH POLY(VINYL ACETATE) COPOLYMER ADHESIVES
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 0039-3630 |
| Online Access: | http://www.viks.sk/chk/studcon_3_02_195_210.doc |
| Abstract: | SUMARRIES. Adhesive support treatments for the conservation of silk artifacts were evaluated by comparing the properties and relative light stability of silk laminates and their components. Samples were prepared by adhering silk habutae, representing the artifact, to a silk or polyester crepeline support fabric with either Appretan MB extra or Lascaux Hot-seal Adhesive 371, both poly(vinyl acetate) copolymer adhesives. Laminates and unlaminated components were exposed to xenon arc radiation and subsequently characterized by measuring colour change, stiffness, and tensile properties. The laminates were stronger, stiffer and sometimes of a different colour than plain silk habutae. The laminates yellowed and exhibited losses in tensile properties when exposed to light, in a manner similar to that of plain silk habutae. The loss of tensile properties and yellowing of the support materials upon exposure to light were at least retarded when covered by the habutae in the laminates. Much less flexible than their components to begin with, the laminates also stiffened more rapidly than their components when exposed to light. CONCLUSION. The laminated fabric structure resulting from adhesion of silk habutae. representing the textile artifact, to silk or polyester crepeline supports, using Appretan MB extra or Lascaux Hot-seal Adhesive 371, exhibited properties in this study that both corresponded to and deviated from those of its components. The colour and tensile properties of the laminates appeared to be closely related to those of the silk habutae component, with some contribution from the support fabrics. Yellowing of the laminates upon light exposure was visually similar to yellowing of plain silk habutae and maybe attributed to the degradation of the silk on exposure to light in a manner that is independent of the support treatment. This conclusion could not be confirmed quantitatively because the colour of the support fabrics was visible through that of the translucent habutae. The tensile properties of the laminates were fairly well predicted by a model that assumes that the two fabric layers bear the load independently. The laminate tensile strength was thus approximately equal to the sum of the strengths of the fabrics at the lowest breaking elongation of those fabrics. The effect of the adhesive is limited to restricting the extension of the fibres, lowering ultimate strength. Thus the tensile strength of the exposed laminates decreased at a rate that closely approximated the decline in strength of plain silk habutae. Results for both colour and tensile properties provide some evidence that the laminate properties upon light aging are not highly affected by the light aging properties of the support materials. Yellowing and degradation of the support fabrics and adhesives were at least retarded when shielded from the light by the habutae. The stiffness of the laminates, however, appeared to be highly dependent on adhesion and bore little relation to the stiffness of the individual components. The laminated fabrics were four to five times as stiff as the sum of the stiffness values of their components. Furthermore, the laminates stiffened upon light exposure at a greater rate than their components. The stiffness of the laminates appeared to be related to the degree of penetration of the adhesive into the silk habutae, but may have also depended on the degree of coalescence or curing of the adhesive layer. The results of this study provide some support for the judgment of textile conservators who have continued to use adhered supports to treat fragile silk artifacts over the last four decades despite problems with particular materials and techniques. Nothing in these results is especially surprising, given the experience of conservators, including the effect of adhesive treatment on the flexibility of silk [6]. The results should be treated with caution, however, since the samples were made with new silk, not the degraded silk found in artifacts usually-treated with adhesive supports. Differences in the chemical and mechanical properties of naturally-aged silk could have a significant effect on the results. Nevertheless, the light to which samples were exposed in this study, xenon arc radiation including near-UV wavelengths, is much more severe than the light levels to which treated historic artifacts w7ould normally be exposed. That silk laminates exposed to such conditions should degrade in a manner so similar to plain silk suggests that this treatment merits further study. |
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| ISSN: | ISSN 0039-3630 |
