Materials and Methods of Preservation Framing - Hinging
The best paste for hinging is made from either wheat starch or rice starch. Most paper conservators use wheat starch; after testing half a dozen paste recipes, at Bark Frameworks we continue to choose rice starch, as we have for decades. We use it because we found that it was smoother than wheat starch paste. We do not add a preservative partly out of concern for our own health but also because some preservatives have been shown to turn brown with time. We make our paste at the beginning of the week, and it is refrigerated; we take out as much as we will need each morning.
Corner pockets are sometimes a good alternative to hinges. They are used most often with photographs but can be used with any work on paper provided that it will be overmatted and that it is small enough and rigid enough that it will not slip out of the corner pockets. At Bark Frameworks we designed and usually make two layered corner pockets, with a Japanese paper inner-pocket extending beyond an over-pocket made of Mylar (archival polyester). We arrived at this method after finding that Japanese paper pockets sometimes tore, especially when framed works are shipped. Mylar is very strong and an excellent material for pockets, but the edges of Mylar are so hard and sharp that we felt they endangered the surface of the artwork held in the pocket. The Japanese paper inner pocket protects the surface of the artwork, and the Mylar outer pocket provides strength. Corner pockets should be attached to the back mat with a bit of room at the sides and top for the artwork to expand.
Regarding Pressure Sensitive Adhesives
All pressure sensitive tapes and adhesives, even those advertised as “archival” should be avoided. The Library of Congress states on its Preservation web site: “In most instances, the object can be hinged with long-fibered Japanese tissue adhered with wheat or rice starch paste. There is no known pressure-sensitive adhesive suitable for hinging an object.” The American Institute for Conservation brochure “Framing Works of Art on Paper” makes a similar statement: “Avoid methods of attaching works of art to back mats such as dry- mounting, lamination, spray mount, rubber cement, or pressure-sensitive tapes (e.g, masking, office, or even those referred to as "archival" or "preservation" tapes). The adhesives in these materials can seep into paper, become discolored, brittle, and difficult to remove.”
There are exceptional cases, such as when the support is made of plastic, in which a pressure sensitive or heat sensitive adhesive must be used. Whenever an unusual adhesive is used, we affix a dated explanatory label to the backing board to help the conservator who must remove it at a later date.
Read More about pressure sensitive adhesives in this article with Margaret Holbein Ellis.