Case Study: Saving the Bison Enlargements

 
 

Worn tan paper with side, face-view of bison These photographic crayon enlargements, associated with William Temple Hornaday (founder of the Smithsonian’s National Zoo), were made on sensitized paper that was later adhered to a linen “canvas” stretched around wooden frames. Brittle paper, handling and water damage, and the deteriorating frames all presented risks to the items’ future. The goal of our treatment was to remove the enlargements from the wooden stretchers, stabilize the damaged areas, and devise a suitable, new mounting method.

The wooden stretchers were removed by first softening the adhesive holding the paper and linen in place, and then, lifting the enlargements away. The linen was then freed from the rusting nails holding it in place, allowing the stretcher to be removed and discarded.

Temporary bridge mends were applied to stabilize the free edges of the tears and losses were removed and replaced with a heat-set repair tissue made of medium-weight Japanese tissue coated with acrylic adhesive. (For more about how conservators choose adhesives, see this resource from the American Institute for Conservation.) Mends were shaped for each tear with a perforating pen, and made sufficiently wide to provide support to the enlargement. The mends were then applied using a heated spatula through silicone release paper to prevent sticking or scorching.

The enlargements were mounted on backing boards of corrugated E-flute board using a series of Japanese paper strips (five inches long by one inch wide, with one end coated in acrylic adhesive) that would hold the objects lightly taut and provide necessary stability. These strips were applied to the verso of the enlargements. Once all the strips were attached, the backing board was put in place and registered. The strips were wrapped around the backing board and fixed in place with cast-out films of acrylic adhesive, reactivated with the heated spatula. Once the enlargements were mounted, areas of the image where the paper was lifting away from the linen backing were tacked back down using more of the adhesive films.

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