CARBON PAPER, a tissue of varying weight coated with a colour, generally carbon, and some waxy medium. It is usually coated on one side but may be coated on both sides for special purposes. For typewriting duplication which is its chief usage it is of course coated on one side only. The paper upon which the coating is applied varies in weight from 4 to Io lb. per ream of 48o sheets 20 by 3oin. and is made from fibres such as rag, chemical wood, manila and jute. As it must be strong and durable it must not contain any ground wood pulp. The coloured waxy material which transmits the duplication is soft so that at least five copies can be made. It is also so strongly coloured and of such durability that a sheet will make at least 12 first carbons that are clear and legible. This coating is composed of waxes such as Japan, paraffin (kerosene) and canauba, and such oils as oleine and rosin thor oughly amalgamated with a colour which in the case of black paper is always carbon or gas black.
In coloured papers the colour consists of an aniline base combined with fatty acids as stearic and oleic or a fat soluble dye dissolved in the oleine or rosin oil present in the mixture. The actual manufacture of carbon paper resolves itself into two pro cesses, viz., the preparation of the coating material and its appli cation to the paper. The waxes and oils are melted in a steam jacketed kettle at a temperature of approximately 300° F and the colour stirred in. Afterwards the hot mixture is passed through a steel plate grinding mill and is then ready for the coating ma chine. This machine, of web-type construction takes the paper in roll form, passing it over the coating roller which revolves in a steam-heated ink foundation containing the hot coating mixture and then over a spiral wire wiper which controls the thickness of the coating. From this wiper it passes over water-cooled rollers which chill and harden the coating, and subsequently it is rolled upon itself at the end of the machine. The roll is then cut into sheets in sizes according to its usage. (N. U.)