The daguerreotypes and ambrotypes in the Princeton University Archives underwent various levels of conservation depending on their condition. Most of the ambrotypes and a number of the daguerreotypes were in good repair and required only basic stabilization -- a minimum of cleaning and the creation of new protective enclosures in which to store the images.
A number of daguerreotypes, however, required more intensive treatment. Over time the seals around many of the daguerreotype packages weakened and allowed air and moisture to come in contact with the silver coated copper plate. This caused the surface to darken, corrode, and become embedded with debris. In some cases the glass protecting the plate had deposits of corrosion. Additionally, previous attempts at cleaning the daguerreotypes -- through cyanide or thiourea, for example -- often caused irreparable damage to the plates.
All of the daguerreotypes receiving conservation treatment were first cleaned using the dry method, their glass cleaned, and resealed. Two groups of daguerreotypes required further treatment. One group, with only minimum corrosion or accretions, was bathed in a water wash. Another group, requiring more intensive treatment, was electro-cleaned. The following sections describe each of these treatments, and some show "before" and "after" examples of treated daguerreotypes.
It cannot be stressed enough that these images were treated by a professional photograph conservator. Much of the earlier damage to these images was caused by untrained individuals who attempted to clean or conserve the daguerreotypes themselves. For information on finding a qualified conservator, individuals are urged to contact the American Institute of Conservators or an archive in their area.