Thermal transfer printing is a process that requires a thermal transfer printer, thermal transfer ribbons, software, and a substrate (i.e. label or tag stock). As the ribbon passes between the heated printhead and label substrate, the wax, wax/resin or resin coating from the ribbon is transferred as an image onto the label. The coating or ink is absorbed into the medial so that the image is part of the label.
Direct thermal printing does not use a ribbon, but uses chemically treated, heat sensitive media designed for direct thermal printers. The media blackens when it passes under the heated thermal printhead causing a reaction in the coating of the label and forms an image.