Whenever I lecture on photo preservation, someone almost always approaches me with a question about a small box or booklike item he found with the family photographs. Some people arrive with one in hand, unsure how to open it. Others know it's a photograph, but wonder what kind it is. The images in these small cases — daguerreotypes, ambrotypes and tintypes — are not necessarily part of every family photo collection, but their beauty makes them valuable family artifacts. If you have one or two in your collection, treat them with care and respect. They are the earliest types of photographs and provide a glimpse into life in the mid-19th century.

Each cased image has several parts: the case, the image, the cover glass, a mat that creates a frame around the image, and something called the preserver, a thin strip of metal with a paper seal that creates an airtight fit of the various pieces. While the glass protects the image's surface from abrasion, the preserver prevents environmental pollutants from contaminating the image.