Reprographic equipment invented in 1780 by James Watt. A sheet or sheets of copying paper would be pressed against original documents, and ink would be transferred. Letter copying presses were made in various forms: roller, bed and platen, and portable models. Presses comprising a platen and base, often a screw press, used to copy an original document. In the 18th century, the original was pressed to a dampened tissue-weight paper, producing a copy transfer; the image was a mirror image of the original, but could be read through the back of the tissue. In the 19th century, the original was often written with a special copying ink that was formulated to allow easy and repeated transfer. For presses of similar design, used to press newly bound books, use "book presses."