A collodion positive (ambrotype) of a seated man, resting his elbow on a book, taken by an unknown photographer in about 1860. The man is wearing a sack suit or lounge suit, an informal style which first appeared in the 1850s. This was casual wear for men who would normally wear frock-suits. The collodion positive process (also commonly known as ambrotype) was popular during the 1850s and 1860s. An underexposed collodion negative on glass was backed with a black opaque coating to create a unique positive image.
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