A user would write on the front of the form, and the pressure from the writing or printing would cause the carbon from each sheet of carbon paper to image on the piece of paper beneath it.
Carbonless Paper Was Invented in 1954.
Carbonless paper is coated with two different types of chemicals: CF (Coated Front), and CB (Coated Back). These chemicals are held in tiny capsules and are released when the capsules are burst by pressure from a pen or printer.
When the CF and CB chemicals interact, the CF chemicals darken causing an image to appear on the CF side of the sheet. One easy way to tell that the CF and CB chemicals are different is that the image appears on only the front sheet; there is no image on the back of any sheets.
Since this type of paper produces an image without carbon, it is called “carbonless paper.”