Old Photography Process: Ambrotype
Ambrotype, the process that replaced daguerreotype was invented in 1850s by Frederick Scott Archer in UK, later (in 1854) brought to US and improved by James Ambrose Cutting and it’s based on wet collodion process.
The process had its peak in 1856-1860, and shortly after, in 1860s, was replaced by tintype.
The name ambrotype was derived from the Greek word ambro, meaning immortal, or imperishable, but it was still an easily damaged photograph, so it had to be specially covered in order to be preserved.
Ambrotypes were much less expensive to produce than daguerreotypes, and therefore easily gained its popularity. Also, for those who didn’t like bright metallic-like structure of daguerreotypes, the new process appeared to be great solution, although ambrotypes might have appeared dull and simple compared to well – produced and properly-viewed images created with Daguerre’s process.
Important advantage that it possessed over the silver daguerreotype was that it did not tarnish.
Ambrotypes are, in fact, negatives that were deliberately slightly underexposed and optimized for viewing as positives when placed against a dark background.
If you magnify ambrotype, it is possible to see that the highlights are made up of silver particles, with very small amount of it in the shadows (almost none), that allow the dark backing to show through. Although they are technically negatives, they are considered direct positives.
Ambrotypes were suitable for hand coloring and it was very common, especially on portraits, using vivid colors to highlight cheeks and lips of the subject, sometimes jewelry and rarely clothing.
They were known for its milky white highlights that gave soft look to images thanks to silver particles formed during development combined with the black background.
The process of making ambrotype is much simpler than, for example daguerreotype. First, glass is covered with a thin layer of iodized collodion than covered with a solution of silver-nitrate. Same as in wet collodion process it is very important that the exposure happens while the plate is still wet.
Depending on the brightness, exposure time varies from couple of seconds to a full minute. After the exposure, the image is developed and dipped into fixer. When dry, the plate is put onto a dark background, usually black velvet, and the negative image appears as a positive.
Another variation of ambrotype is ruby-ambrotype, made on reddish colored glass, and it eliminated the need of dark backing. There are three different glass variations in the ambrotype. Early images used two pieces of glass glued together. The image was put between them.
This technique was used from 1855 to about 1857. Later, from 1858, single pane of glass was used exclusively, and the same year ruby colored glass (dark green as well, but rarely) made its appearance.
Final part of the process is usually covering the back, or the front of the plate, giving it different effects depending on which side is darkened with black lacquer.
Image was very delicate, fragile and it needed to be protected. All ambrotypes were protected similarly as daguerreotypes.
Protective pack consisted of a sheet of cover glass and a brass mat, which are folded into a thin preserver frame and placed into a protective case. Common sizes were 1/4 Plate – 3 1/4″ x 4 1/4″, 1/6 Plate – 2 5/8″ x 3 1/4″ and 1/9 Plate – 2″ x 2 1/2″. Bigger ambrotypes exist, but the examples of an ambrotype on a whole plate are extremely rare.