Carbon paper (originally carbonic paper) is paper coated on one side with a layer of a loosely bound dry ink or pigmented coating, usually bound with wax. It is used for making one or more copies simultaneous with the creation of an original document. Manufacture of carbon paper was formerly the largest consumer of montan wax.
Carbon paper is placed between the original and a blank sheet to be copied onto. As the user writes or types on the original, the pressure from the pen or typeface deposits the ink on the blank sheet, thus creating a "carbon copy" of the original document. This technique is generally limited to four or five copies.
As the ink is transferred from the carbon paper to the underlying paper, an impression of the corresponding text is left on the "carbon" where the ink was removed. A single piece of carbon paper can be repeatedly reused until the impression grows too light. An interesting student experiment is to create a sort of imitation carbon paper by rubbing pencil lead on the reverse side of a piece of paper, placing this on top of a second piece of paper (with the carbon between), and then writing on the front side of the top sheet.
Carbon paper used to create sensitive documents can be subjected to forensic analysis and is thus a concern within information security, so it must be shredded or otherwise destroyed to maintain security.
Carbon paper has been mostly superseded by electronic means such as photocopying, though it is still, although rarely, used to make copies of typewriting. Also, a carbonless copy paper is still used in situations where instant copies of written documents are needed. Examples of this are receipts at point of sale (though they have mostly been relegated to being backups for when electronic POS devices fail) or for on-the-spot fine notices, duplicate checks, and some money orders (though the United States Postal Service has recently converted to an electronic format), and tracking slips for various expedited mail services requiring multiple copies.
There have been some experimental uses of carbon paper in art (as a surface for painting)[1] and mail art (to decorate envelopes).[2]