The infrared wavelengths produce heat. Thermal plates are coated with special polymers that react to the heat of a specific wavelength within the infrared band. Heat from the infrared laser beam must reach a required level in order for the reaction to occur. Heat below the required level will not affect the plate.

One benefit of using thermal plates is that they can be handled in visible light because they are sensitive only to infrared light. Another benefit is the either or aspect of the exposure. The plate can be imaged only if the heat produced by the laser is great enough, otherwise nothing happens. The plates also provide a slightly sharper dot than the dot generated by a visible light system.

Two types of thermal plates that are available are ablation plates and cross-linking polymer plates. Ablation plates are those in which thermal lasers actually ablate (remove) areas of the emulsion while the plate is being imaged. After exposure, a residue is left on the plate over the ablated areas, which must be washed away. Cross-linking polymer plates contain emulsions that consist of two resins that are cross-linked when the plates are exposed to the proper wavelengths of infrared light.