CONSERVATION OF CHINESE SHADOW FIGURES: INVESTIGATIONS INTO THEIR MANUFACTURE, STORAGE, AND TREATMENT
4 REHOUSING AND SILICONE MYLAR
Since the oil has ethnographic significance and cannot be altered or removed, choosing appropriate and compatible storage materials for rehousing is a priority. Several attempts at creating safe housing for the collection were undertaken in the past. In spite of good intentions, these campaigns have complicated storage and condition issues. A variety of materials were used as interleaves, including silicone release paper, acid-free tissue, brown Kraft paper, Mylar, and plastic. The figures stuck to all of these surfaces. Requirements for the new storage environment included controlled temperature and humidity conditions as well as storage on a surface that is nonstick, nonreactive, and nontextured.
We considered vertical storage, Teflon surfaces, and silicone-coated Mylar surfaces. Vertical storage was impractical due to space considerations. The thought was that the puppets would hang from a horizontal support so that none of their surfaces touched any storage material. An additional concern with this concept was distortion of the skin over time.
During this investigation, which began in 1994, the Teflon we were considering was in a thick sheet or tile form, and the cost of this product was too high. At the time, we were not aware of the possibilities of using Teflon films. Teflon tape (plumber's tape) was considered but later eliminated as an option due to the narrow strip form in which it was supplied. Since then, we have been made aware of the use of such film supplied in a wider form (Odegaard et al. 1997). The film can be purchased in widths up to 12 in. and is a viable option for long-term storage of artifacts with tacky surfaces. Initial investigation into the material indicates that its release level is not as high as necessary for the high tack of the puppets.
At the time of the shadow puppet rehousing project, our focus went to silicone-coated Mylar as a practical choice. During our investigation into this material, we realized that the silicone coating on the Mylar on hand in the conservation laboratory was not permanently “adhered” to its substrate and was readily removed by a range of solvents. For long-term storage, such qualities were unacceptable since the eventual loss of the nonstick properties of this material when in contact with the soft oil seemed too risky.
Further research into the range of technologies involved in the manufacture of the product led to the discovery of several interesting facts. Many companies purchase the raw Mylar, using Dupont Mylar A or D, and apply the silicone coatings using several polymerization techniques, the major ones involving UV or heat-curing technologies. Conflicting opinions from the suppliers about the effect of these processes on the final physical qualities of the coating were common. Most claimed there are varying levels of transfer of the coating to whatever material is laid upon it, the UVcured coatings transferring the least and the heatcured coatings having a higher possibility of transfer. Requirements for the storage surface for the shadow puppets included a film with a low transfer potential and medium or high release levels. A coating company named Douglas Hanson uses a UV activation polymerization technique that results in a product that meets these requirements, and both Conservators' Products and Talas distribute this product.
Rehousing the collection involved preparation of each shelf by lining it first with acid-free corrugated board and then with the Douglas Hanson siliconecoated Mylar. Puppets were laid onto the Mylar surfaces and pinned in position through preexisting holes in the carvings with map pins that had been coated with an isolating layer of Paraloid B-72. The pins were used to keep the puppets from sliding out of place when trays were pulled out of their cabinets. This event was common on the slick Mylar surface.