Tintype or ferrotype uses the same process and principle as an ambrotype. An ambrotype is a negative on glass that appears positive when backed with an opaque material. A tintype is a collodion negative on iron that has been coated with black paint or enamel to make it appear positive. Tintypes were exposed while the collodion coating on the metal was still wet. They were immediately processed, producing a type of “instant photo.” Being more durable and cheaper to make, they were not usually encased. A good magnet will distinguish between the two types.
