Wet Plate Process

Ambrotypes, which resembled but cost less than daguerreotypes, were made using the collodion wet plate process that was also used to make negatives. The name “ambrotype” was devised by Philadelphia daguerreotypist Marcus A. Root in 1855, from the Greek ambrotos, meaning “imperishable.” Although James Ambrose Cutting of Boston received three patents relating to the collodion process, he was not the inventor.

Ambrotypes are made from underexposed or underdeveloped collodion negatives, made via the collodion (wet-plate) process: first, the glass plate must be perfectly cleaned. Next, collodion, a viscous solution of nitrocellulose dissolved in alcohol and ether, combined with potassium iodide is poured onto the glass plate until evenly coated. The glass is then submerged in a solution of silver nitrate, which reacts with the potassium iodide, making the plate sensitive to light. The sensitized plate is then placed in a camera and exposed. After exposure, the plate is developed in pyrogallic acid. A fixer of sodium thiosulfate, or hypo, is necessary to keep the plate from undergoing further exposure. The plate is then washed, dried, and ready for printing.

It was discovered that placing a dark or black background behind the glass plate made the negative appear positive, so users would paint the back of the plate black, place black paper or velvet behind the plate, or even apply the collodion to dark-colored glass, such as ruby glass. Quickly and cheaply, the collodion negative would become an ambrotype.

Ambrotypes were presented in the same small leather, paper, or thermoplastic (“Union”) cases as daguerreotypes, but cost a fraction of the price. Consequently, portrait photography became accessible to those who could not afford daguerreotypes, and the world’s nascent photographic record widened.

Tintypes are made using the same collodion, or wet plate, process that was invented in 1851 and became popular for producing negatives and ambrotypes on glass foundations. Because of their lower cost, shorter exposure times, and greater durability, tintypes eclipsed both the daguerreotype and ambrotype for portrait photography.

In 1856 Hannibal L. Smith patented a process that used a thin sheet of iron that was blackened (or japanned) with asphaltum and used as the support for the collodion emulsion. Originally known as the ferrotype and then advertised as the melainotype, the process became most popular as the tintype, a misnomer, as no tin was used.

To produce a tintype, a japanned iron plate must be perfectly cleaned. Next, collodion, a viscous solution of nitrocellulose dissolved in alcohol and ether, combined with potassium iodide, is poured onto the metal plate until evenly coated. The plate is then submerged in a solution of silver nitrate and becomes light sensitive when the silver combines with iodine to form light-sensitive silver iodide within the collodion emulsion layer. The sensitized plate is then placed in a camera and exposed. After exposure, the plate is developed in pyrogallic acid. A fixer of sodium thiosulfate, or hypo, is necessary to keep the plate from exposing further. The plate is then washed and dried.

Tintypes made portrait photography widely affordable. Being on metal, tintypes were much more durable than ambrotypes, which allowed them to be sent through the mail and carried on a person, attributes that made them popular during the Civil War.