Thermal copier
Thermal copiers are very simply constructed, obsolete copiers and require the use of thermal copier paper.
The one-sided original must have strong black-and-white contrasts and, when in contact with the heat-sensitive paper, it is directed past a strong light source (rod-shaped halogen lamp ) facing away from it .
As a result of the local warming of the original, especially in the dark (printed) areas, the thermal copy paper blackens in these areas and creates a positive of the original.
Thermal copiers therefore only work poorly with thick originals. The conveyor speed can be varied to adapt to the paper thickness and the contrast of the original. Thermocopies do not last long because they are light-sensitive and cannot tolerate high temperatures. Thermal copiers have now been replaced by the Xerox process .
In the GDR , thermal copiers were the only freely available copiers.