Thermal printers use two types of printing technologies: direct thermal and thermal transfer printing.
Traditional thermal printers use direct thermal method by pushing electrically heated pins against heat-sensitive paper (thermal paper). The coating on the thermal paper turns black in the areas where it is heated, producing characters or images. Direct thermal printers have no ink, toner or ribbon. These printers are durable, easy to use and cost less to print than other printers. However, the thermal paper is sensitive to heat, light, water, and abrasion and the text and images may fade over time.
In thermal transfer printing, a thermal print head applies heat to a heat-sensitive ribbon, which melts ink onto paper and a wide range of materials to form text and images. The printouts can be extremely durable and can be stored over long period of time.
Thermal printers are often used in cash registers, ATM and point-of-sales terminals. Direct thermal printing was used in some older fax machines before the 21st century. However, these old models are now replaced by new machines which use laser and inkjet printing. Thermal printing is still considered as the best technology for bar code printing because it produces accurate, high quality images with exact bar widths. Some portable printers and most label printers still use thermal printing method.
Thermal printer is not the same as thermal inkjet printer. The latter uses inkjet print technology by heating liquid ink to form vapor bubble, which forces the ink droplet onto the paper from the nozzle.