Hot stamping is a dry process, a very permanent and durable process. The image is thermally fused to the substrate. Even after years of outdoor exposure or complete failure and wash out of the pigment over time, a readable image often remains on the part. Hot stamping upsets the molecular structure of the material with heat and surface melting. Thus combining the heat activated adhesive coat of the foil directly with the substrate being decorated.
Hot stamping is better described as a die selective heat transfer process. The transfer only occurs where the die contacts the part. In its simplest form, hot stamping utilizes a heated die generally mounted to the upper platen of a press. The multi-layer foil is compressed between the die and a part, which is fixtured on the press work table. The foil is held sandwiched between the die and the fixtured part for a period of time known commonly as dwell time. At the completion of the dwell time, the press opens and the pigment layers of the foil have been bound to the part by heat and pressure only where the die made contact. The foil carrier is then stripped upward from the part. During the stripping operation, the pigmented layers of the foil will separate from the carrier only in the areas where heat and pressure have been applied. The foil web is not actually punched out in the die contact areas, rather, specific layers are activated by the heat and pressure to adhere to the part and release from the web material that the foil is made on which is usually polyester film. After printing, the spent foil will show areas of clear carrier where the pigment has been transferred off.