Page:Paper and Its Uses.djvu/61

Rh a good finish. An ingenious overhead railway carries the web forward in a series of loops supported on a series of rods, hot air driven forward by mechanical fans effecting the drying. If the paper is two-sided art, it is reeled and the operations repeated on the other side of the paper. As the coating is slightly thicker at the edges of the web, these edges are trimmed off, and the web goes forward for one or more journeys through the super-calender rolls. Dull art and papers with a specially high finish receive slightly different treatment, the surface in all cases being made perfectly smooth in order that the finest half-tones may be printed successfully.

Chromo papers are usually coated on one side only, and the body paper is stouter than that used for art papers. Used largely for lithography, the paper must be as free from stretch as possible. This is obtained as described in the chapter on the reduction to pulp, by using soft fibres, sharp beater knives, and cutting up quickly, this treatment producing what the papermaker knows as "free" pulp, as distinguished from "wet" pulp, which, owing to prolonged treatment, combines with some of the water and actually becomes "wet." The surface of chromo papers may be dull or highly glazed.

Surface coloured enamelled papers are used largely by box-makers, for labels for packets of various commodities, and also as end papers for books. The coating and body paper are thinner than for art papers, the colour is obtained by the use of a pigment or an aniline colour, and the coating and after-treatment are exactly as in the case of art papers. Flint-glazed surface papers are used for the same purposes as surface-enamelled papers, and have a hard burnished surface obtained by a stone burnisher travelling