_Color._ The only really indelible color is black; that is because carbon is the basis of the color. The colors which are used are powders which have been ground as fine as possible. They are mixed in proper proportions with oils and waxes. Formerly the mixture was applied by hand, but great strides have been made in machinery for automatically applying the color evenly to the paper. It is important that the color or pigment be applied evenly to the paper and that it penetrates the fiber. Unless the paper retains the pigment, the carbon paper will not wear properly. The longer the color adheres to the paper, the longer it can be used. _Finish._ The finish of carbon paper is the factor which is so little understood by the public. Carbon papers are finished with soft, medium, and hard finishes. The first will hardly rub off on the hand under pressure, the next will rub some, and the soft finish will smudge if pressed against the hand. Each finish is intended for a definite use, which will be explained later. The manifolding power of carbon paper depends absolutely on the typewriter itself, the hardness of the rubber roll, the touch of the operator, and the weight of paper, and lastly, the finish of coating on the paper. Two operators on the same typewriter can secure totally different results because one will have light, and the other heavy, touch. The regular rubber rolls which are furnished with typewriters are medium hard—in six months or a year they gradually grow harder, eventually becoming as hard as slate. If a typewriter is to be used for regular work as well as heavy manifolding, it should have two different rolls, one for each kind of work. There is no reason for using a medium hard rubber roll on the machine, getting poor results, and then blaming the carbon paper. Use a hard rubber roll on the machine and there will be no difficulty. Some makes of machines have interchangeable rolls (known as _platens_) which are very useful. It is the work of a minute only, to remove one and place the other on the machine. _Four-Pound Paper._ This class of carbon paper has a heavy, sensitive coating, and is intended for heavy manifolding—for making from five to twenty copies. Soft-finish carbon papers are always used where heavy manifolding is to be done. The finish of the paper which is being written upon is also a factor. Papers with a hard finish—that is, a shiny surface—do not allow the color of the carbon paper to take hold, and yet a paper with the soft finish will allow the color to spread, and make a poor copy. This class of paper is also used for making a few copies on very light-stroke machines like the Hammond. _Seven-Pound Paper._ This weight of paper is adapted for making from one to five copies. Being heavier than the four-pound, it will wear longer. If coated heavily it will give more impressions than if lightly coated, but the impressions will not be as clear and clean.