Copiers typically feed paper from a roll, where it is given a static electric charge, after which it is exposed to light reflected from the original document, and focused through a lens; zinc oxide particles either preserve or discharge the electric charge, depending on the amount of light reaching them.
Typically, the paper is finally sent to an output tray where any remaining dispersant evaporates, leaving copies with a faint "kerosene" odor.
Subsequently, many office machine companies, including SCM (Smith Corona Marchant), Savin, etc., introduced copiers that utilized this technology.
Electrofax fell out of favor when other copier technologies could produce markedly better quality copies at less expense.
By comparison, electrofax suffered a number of drawbacks, including: weak blacks in the image (most machines could only produce a dark gray), dampness and odor of the copies, the need for special paper, and multiple-bottle liquid toner replacement.