Thermofax and Models

Thermo-Fax (very often Thermo fax^[1]) is 3M's trademarked name for a photocopying technology which was introduced in 1950.^[2][3] It was a form of thermographic printing and an example of a dry silver process.^[4] It was a significant advance as no chemicals were required, other than those contained in the copy paper itself. A thin sheet of heat sensitive copy paper was placed on the original document to be copied, and exposed to infrared energy. Wherever the image on the original paper contained carbon, the image absorbed the infrared energy when heated. The heated image then transferred the heat to the heat sensitive paper producing a blackened copy image of the original.

Model 12

The first commercially available Thermofax machine was the Model 12. The 'layup' of the original and the copy paper was placed on a stationary glass platen and an infrared lamp and reflector assembly moved beneath the glass, radiating upwards. The layup was held in position by a lid with an inflatable rubber bladder that was latched down by the user.

Model 17

In subsequent versions, beginning with the Model 17, the layup was fed into a slot, and continuously exposed as it passed the lamp and reflector. The Model 17 and successors were table-top machines, approximately the size of a typewriter from the same era.

Q system

A variation of this technology was a billing system called the Q System, which was typically used by medical and dental offices. A 'master' composed of a sheet of heavy backing paper and a thin sheet of ruled paper attached to it at the top edge was created for each patient. Billing entries were then made in pencil on the thin sheet for each patient visit. To create a billing copy, a sheet of heat sensitive paper was inserted between the backing and the entry sheet and passed through the ThermoFax machine,a Model 47being the most commonly used.