The Preservation Unit has been involved in our Wellcome funded project to catalogue and preserve the papers of Professor Guido Pontecorvo. The project assistant, Karyn, has been absorbed not only by the whirl of events and facts of the past life of Pontecorvo but she also physically felt the connection with photographs through the smells of chemical components coming from inside the album. The photo album not only tells a story about past time but also is a source of information about materials for paper conservator in Preservation Unit.
From a conservation point of view, a photograph is a complicated, structural material which consists of multiple layers. Each layer contains different substances which behave in a variety of ways. The support layer may be glass, plastic film, paper or resin-coated paper. The emulsion or binder layer, mostly commonly gelatine (but also albumen or collodion), holds the final image material or image-forming substance to the support. Paper for ink jet prints is often coated with synthetic materials. Final image materials, made of silver, colour dye or pigment particles, are usually suspended in the emulsion or binder layer.
This complex structure can make certain types of deterioration untreatable: what might be beneficial to one layer may be harmful to another. Identification of different types of photographs requires knowledge of the history of the photographic process. This information is needed not only for cataloguing but also for making informed preservation decisions; this is why it is important to do a conservation assessment before each treatment. In the late sixties, photo papers began to be made with a plastic (polyethylene) laminate on both sides of the sheet. These papers are called resin-coated or “RC” papers (see figure 1)
Some of the photographs in the Pontecorvo collection were stored in a commercially available album with reddish brown vinyl covers, made up of 48 self –adhesive pages with clear plastic sheets covering each page. Many of the images have valuable captions on the reverse identifiying people and places.
The album was made of poor quality materials and the adhesive on the album pages was brittle and yellowing at the edges. Self-stick pages secure photos to the album pages, but these self-stick pages are coated with an adhesive that stains the photos and fades some type of photographs over time. In the short term the adhesive becomes very tacky, making it difficult to remove photos without damaging them. In addition, in the long term, the adhesive discolours to an unsightly dark yellow.
For the storage of photographs a special quality album was prepared with conservation quality paper and polyester sleeves. The original order of the photographs was one of the most important principles when considering repacking the material. Photographs attached to self-stick album pages were removed by inserting a scalpel under the edge of the photo and gently separating the photo from the page.
All photographs were carefully transferred to the new album pages. The work is now completed and the photographs are placed in the order reflecting their original place in Pontecorvo’s album.
Because of the extensive date range of the Pontecorvo collection the advances in Photographic technology can be seen clearly through study of the photographs contained in this album.
Categories: Archive Services (GUAS)