The induced absorption bands in the material, caused by F-centers created by electron bombardment, can be returned to their non-absorbing state, usually by light and/or heating.
Using conventional deflection and raster formation circuitry, a bi-level image could be created on the membrane and retained even when power was removed from the CRT.
This CRT replaced the conventional light-emitting phosphor layer on the face of the tube screen with a scotophor such as potassium chloride (KCl).
Potassium chloride has the property that when a crystal is struck by an electron beam, that spot would change from translucent white to a dark magenta color.
The image on KCl can be formed by depositing a charge of over 0.3 microcoulomb per square centimeter, by an electron beam with energy typically at 8–10 keV.
Its advantage against KCl is its higher writing speed, less fatigue, and the F-centers do not aggregate, therefore it is possible to substantially erase the screen with light only, without heating.