The Conservation Unit is responsible for the conservation and preservation of the analogue materials held by the Library. Conservation treatment includes the repair of damaged items and the strengthening of fragile ones. Without this specialised intervention, many of the vulnerable items could never be digitised or presented to readers. Preventative conservation involves a series of activities which aim at preventing damage and stabilising condition, in order to extend the lifespan of the collection items.
When executing conservation treatment, international ethical guidelines are followed. These include:
- an emphasis on the least possible intervention to safeguard the historical characteristics of the object
- the use of archival quality materials that will not adversely react with the object
- the use of totally reversible techniques
- the use of current and acknowledged information and techniques
Traditional bookbinding skills are used side by side with modern scientific techniques. The acidity of paper is tested, and documents and books can be deacidified. The conservators repair and treat a wide variety of archival materials to a very high standard. These include:
- paper and parchment
- antiquarian and modern bindings
- wax seals
- tithe maps
Conservation of Acetate Film
Vinegar syndrome is the popular name for degradation of negatives on cellulose acetate film bases. Though far more practical than their nitrate predecessors, cellulose acetate based films are not indestructible. Problems arise when the cellulose acetate which supports the photographic emulsion starts to degrade, producing acetic acid ("vinegar") as a by-product. Cellulose acetate is a modified version of cellulose. It can, depending on temperature, relative humidity and acidity, attempt to revert back to its original form. This in turn produces acetic acid within the plastic which diffuses to the surface, causing odour, embrittlement and, most damagingly, shrinkage of the film base. This shrinkage leads to the film emulsion, undamaged by the acid, separating from the film base, causing the characteristic channeling. The process of deterioration can be slowed right down by vacuum sealing and freezing the affected negatives.
The conservation department within the Library is therefore undertaking the challenging task of “treating” these affected negatives. Using a technique developed by Chris Woods, a Research Fellow at the University of the Arts London and Ian and Angela Moor at the Centre for Photographic Conservation, the gelatine and cellulose layers that cause the damage to the negative are removed and the image pellicle re-hydrated and re-suspended in inert polyester housings.
This treatment means that Vinegar Syndrome can no longer damage the image pellicle and that the negatives no longer need specialised freezing storage. It is hoped that all the cellulose acetate negatives in the Library’s collection can be treated in this way. In most cases the treatment returns the negatives image to its original state and eventually these treated negatives will be re-digitised so that users have access to a higher quality image.