Initially called a "ferrotype," the tintype is a one-of-a-kind photograph made on a thin sheet of iron (not tin) coated first with black or dark brown lacquer, then with a layer containing light-sensitive silver salts. The tintype image is actually a negative, but appears positive against the dark lacquer background. The tintype's main subject was the portrait, often made inexpensively by itinerant photographers, and mounted in simple paper enclosures. Tintype images usually appear creamy, with a limited tonal range, and were often embellished with paint to accentuate the sitters and their clothing, and to cover the backgrounds. Tintypes were popular from the mid-1850s into the early decades of the twentieth century.