The aim of archive conservation is to alter the item as little as possible. We use the most suitable methods and materials so as not to disguise any written evidence. The materials used in conservation work need to be of the best quality so that repairs are not required again some years later. 'Like' is repaired with 'like' to ensure that the repair and the original react together if subject to environmental changes. We aim to produce a sympathetic repair which does not cause stress within the document. This is so that we can reverse the process if it starts to cause problems.