THE USE OF SPRAYED POLYVINYL ACETATE RESIN MIXTURES IN THE MOUNTING OF TEXTILES
Paul Himmelstein, & Barbara Appelbaum
The method described above offers several advantages over previously described heat-seal mounting techniques. Polyvinyl acetate resin has been used by conservators for over forty years; its excellent aging and working properties are well known.10 Because it is available in several viscosity grades with different melting points, mixtures can be prepared with a wide range of softening points.11 The softening points of AYAC and AYAA are 89.6 and 150.8 degrees F. respectively. By changing the proportions of the mixture, and thereby the softening point, and by varying the application of heat, bonds of varying strengths can be obtained.
The actual exposure of the textile to heat is not severe. When using an equal mixture of AYAC and AYAA, on a silk embroidered textile being mounted to cotton, actual measurements were taken of the temperatures involved. The iron was set at around 140 degrees (measured with a surface temperature thermometer). Paper thermometers set at several places under the mounting fabric read between 110 and 120 degrees F. after the piece had been mounted. This compares favorably with the figure of 80 degrees C. (176 F.) given by Beecher for his heat-seal method using an internally plasticized vinyl acetate-vinyl caprate copolymer emulsion.12 The figure for the PVA heat-seal could be lowered further by changing the mixture.
Maximum flexibility combined with intimate overall support can be provided for extremely deteriorated textiles by using an adhesive-coated net. The use of a closed-weave fabric produces slightly less flexibility. The use of a sprayed rather than brushed or rolled layer of adhesive prevents the stiffening of the support fabric that would result if the threads were impregnated with resin. The resulting package, made up of the original and its support, retains all the qualities of a textile and can be mounted in a variety of traditional ways. Where complete immobilization is not necessary, the original plus support can be handled for display in the same way as the undeteriorated original.
Because the adhesive layer has very little gloss until ironed, it produces no visual disturbance in textiles with very open weave or sizeable voids. If the textile is mounted onto a fairly transparent net, general compensation can be carried out by laying a fabric of appropriate color under the net. If the textile is mounted onto an opaque fabric, the support itself can be colored appropriately.
If it becomes necessary to remove the textile from the support fabric, several alternative methods can be used. In the case of textiles which, like the Matisse scarf, are not deteriorated but have been heat-sealed for other reasons, the textile can simply be pulled away from the support, leaving no resin on the back of the textile. In other cases, toluene or other appropriate solvents can be sprayed onto the reverse of the support, and the support fabric can then be peeled away. If a hot table is available, heat can be used to reverse the mounting process.
The final mounting method used for the flag and the scarf was described in an article by the late Louisa Bellinger.13 It is excellent for textiles supported by either sewing or heat-seal adhesives. The textile is protected front and back from dust, mechanical damage, and ultraviolet light, without being completely sealed off from the outside environment. Constant tension is maintained throughout the treatment procedure, since the fabric supporting the textile does not have to be transferred to a second support for display. At the same time, the textile remains easily accessible for further treatment, cleaning of the Plexiglas, etc. The Plexiglas is automatically held away from the textile without additional liners or spacers being needed. If desired, a window can be made on the mounting fabric to allow viewing of the reverse of the textile. The whole package can also be inserted into a conventional frame.
We feel strongly that it is a conservator's responsibility to see the treatment of a textile through to a point where the textile is safe from careless handling. The proper mounting of a textile onto an auxiliary support, regardless of the method, cannot in itself insure the future safety of the original. If nothing remains to be done to permit display, then the textile is that much safer from framers, museum technicians, and other personnel who are often untrained in the special problems of textiles. The final mounting package we have described assures that this is the final result and provides the additional protection required for the preservation of the object.
This heat-seal technique, as all previously described heat-seal methods, is only suitable for thin textiles. Because there is attachment only to the back layer of fibers, with thicker textiles there would be a tendency for separation to occur at points of stress between adhered and unadhered fibers. This is especially true of multi-layered textiles such as Paracas embroideries. In some special cases, sewing can be combined with a heat-seal method.
While the use of sprayed polyvinyl acetate resins is not suitable for certain types of textiles, it is adaptable to a wide range of textile conservation problems and can be combined with sewing where appropriate. In the past, the spray gun generally has been used by paintings conservators. Like the vacuum hot table, which was developed for the treatment of paintings, but has been used successfully in the treatment of textiles,14 the spray gun may prove to be an extremely useful tool in textile conservation. It is very important for conservators in a particular specialty to familiarize themselves with the techniques and tools of other specialities, so that in the future they may have the widest possible range of treatment techniques at their disposal.