By 1860, glass-mounted photos were largely supplanted by the more durable “tintype,” in which a photo was chemically burnished onto sheet iron through a hazardous process involving mercury.  

The tintype saw more uses and captured a wider variety of subjects than any other photo medium of this period.  In the hands of  itinerate photographers working out of covered wagons, tintypes were relatively easy to produce, making them the primary means of visually documenting the Civil War and American life in the postwar era of reconstruction.

below: three American tintypes taken on-location, ca.1865-70.

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above left: American tintype, "Nellie McGregor - 1863."  Early examples of tintypes were mounted in hard cases just like ambrotypes and daguerreotypes, but   inexpensive cartouche-style paper sleeves quickly became the norm.
above right: Because of their willingness  to hold a pose, dogs dominated the first decades of pet photography, but a number of amenable cats also made an appearance in early portraits, such as this tintype from around 1870.