Recognizing Cased Images
In the early days of photography an image was often put in small wooden or plastic case. The Daguerreotype was made on an extremely delicate and fragile copper plate coated with silver. In order to protect the image from oxidation the plate was sealed into a glass "sandwich" to form what is called an image packet, which was then placed into a small wooden case for protection.
A daguerreotype image outside its packet can be damaged merely by breathing on it. Therefore, the case was required to protect the glass image packet from being broken. An alternative to the Daguerreotype, called the Ambrotype appeared in the 1850s. It was a collodion image made on a glass plate. Because of the glass plate and cover plate used to protect the image, Ambrotypes were also put into a wooden case. The cheap tintype image was frequently sold in a fancy wooden case to make it appear like the more expensive Daguerreotype or Ambrotype. Because of this, a common mistake is to think any cased image is a daguerreotype. It appears the marketing skills of gallery operators is still at work over a hundred years later. Most cases were constructed from small pieces of wood milled by hand and assembled in a factory. The case was usually given a decorative leather cover with embossed design and had a felt or velvet pad in the door facing the image and a small latch on one side. Surprisingly, there were cases made from an early molded thermoplastic. These are called Union Cases and are collected by some for their beauty and uniqueness alone without any image.
The Gutta Percha Myth
Often, cases made of early thermoplastics are mistakenly referred to as being made of "gutta percha." Gutta Percha is a rubber-like material derived from the dried sap of sapodilla trees, which are found in East Asia. It was one of the first of the natural plastics to be exploited by people. The material was used for making golf balls starting about 1848 and lasting well into the 1900s. And for waterproofing early transatlantic telegraph cables. If you want the facts on this, please see Union Cases : A Collector's Guide to the Art of America's First Plastics because I am not an expert in this field of collecting.
Recognizing Cased Images
The following paragraphs describe each type of image and give distinguishing characteristics.
Recognizing the Daguerreotype
The Daguerreotype has one of the most unique and recognizable images throughout the whole history of photographic processes. Because the daguerreotype is made on highly polished metal plate, the image has a reflective, mirror-like appearance. The image is often likened to one of the small holograms you might see in a child's set of stickers or affixed to a credit card. Like the hologram, the Daguerreotype image is only visible from certain angles. No other photographic image has the mirror-like non-image areas or "floating" hologram-like image of the daguerreotype. The Daguerreotype is a unique one-of-a-kind image not involving a negative and the image is a mirror-image (reversed left to right) of the original photographed scene.
Recognizing the Ambrotype
It can be very difficult to tell the Ambrotype and tintype apart. Many tintypes are sold as Ambrotypes Because the they generally fetch a higher price as an antique or collectible image. On the other hand, many are sold by mistake. Both the Ambrotype and the Tintype share the same whitish-gray low-contrast collodion image. The difference between the two processes is that the Ambrotype is made by coating a plate of glass with collodion and the Tintype is made on a metal plate. If the Ambrotype is removed from its case, the glass plate can be readily seen. Also they Ambrotype may show a slight shadow or "three-dimensional" look because the glass plate may lift the image up from the background. The Ambrotype is a unique one-of-a-kind image not involving a negative and the image is a mirror-image (reversed left to right) of the original photographed scene.
Recognizing the Tintype
The Tintype is relatively easy to identify. Because the Tintype image is made on an iron plate, it will attract a magnet. Take a small magnet, such as found on a refrigerator, and see if the plate attracts it. If it does, you have a Tintype. Also, by removing the image from its case, you should be able to see the metal plate. The Tintype plate is also very light weight compared to the heavy glass Ambrotype plate.
Early Thermoplastic Cases
If you want to know just about everything there is to know about early thermoplastic photograph cases (commonly called Union Cases), you should pick up a copy of Union Cases : A Collector's Guide to the Art of America's First Plastics, co-written by author and collector Clifford Krainik. This book shows off the both author's years of experience and meticulous research into the history of the first commercial plastics and their use in the unique decorative cases used to safeguard the delicate photographs of the nineteenth-century. Features outstanding photographs of many types of Union cases. Whether you are a collector of Union cases or collect cased images and want to know more, you will find this a reference you return to again and again.
Union Cases : A Collector's Guide to the Art of America's First Plastics by Clifford Krainik, Carl Walvoord.
Collector's Guide to Early Photographs by O. Henry Mace.