thermal printer A type of printer in which the image is produced by localized heating of paper that has a very thin thermosensitive coating containing two separate and colorless components. When heated the color former melts and combines with the previously colorless dyestuff to make a visible mark. Various colors are possible but blue and black are the most common. Blue toning paper allows higher print speeds but the image fades with time and is not compatible with some photocopiers. Black toning paper requires higher temperatures and pressure at the print head – thus causing greater wear – but fades less quickly and has a longer shelf life. The printers can be either serial or line printers. See also thermal transfer printer, electrothermal printer.

ther·mal print·er • n. a printer in which small heated pins form characters on heat-sensitive paper.