In recent years, water-marks have been used as a means of designating the manufacturer, rather than for the purpose of distinguishing the paper itself. The crane, for instance, appropriately designates the paper made by the Cranes, a family whose name has been long and prominently associated with the industry in this country.
♦Paper in the mechanical arts♦
The many and divers uses to which the paper product can be put have opened up a practically unlimited field to the originality and genius of the paper manufacturer, who has learned to so manipulate his raw materials as to permit of the finished product’s being substituted for iron, lumber, cloth, etc., and in many cases it better serves the desired purpose.
As has already been stated, paper, considered in reference to its general quality and the method of manufacture, falls into three main divisions, viz., writing, print, and wrapping papers, but these divisions give only an inadequate idea of the many varieties. The most of these are obtained by the varying manipulations of paper already complete in one or another of the three forms. The various kinds of boards furnish an interesting example of one of the most comprehensive classes of paper. Bristol board, so named from the place where it was first manufactured, cardboard, pressboard, binder’s board, trunk-board, and the like, all hold very prominent positions in this, one of the most important of industries. The heavier of these boards are made by combining as many sheets of paper as are necessary to give the desired thickness, and then by using paste or applying hydraulic pressure, consolidating them. The number of sheets used is indicated by the word “ply,” used as a suffix, as two-ply, three-ply, four-ply, and so on.
Like other articles of the commercial world, papers take their names from varying circumstances, and there is a large class whose designations have been derived from the materials or processes employed in their manufacture, as well as from the purposes for which they are to be used.
♦Coated paper♦
Coated paper, or paper having an enameled surface, is made by applying a mixture of clay and glue to ordinary paper. When referred to in connection with coated paper, this ordinary paper is called raw stock or body paper. It is manufactured in the regular way, but is made slack-sized and sent to the coating factory in web or roll form, and before it has been calendered. The clay used is pure kaolin or china clay, formed by the disintegration of feldspathic rock. The clay is largely found near Cornwall, England, and the pure white variety, principally used, is known as leemore clay, while the finest is called blanc fixe. The clay is ground to the fineness of fine wheat flour and mixed into solution of about the consistency of milk. Its purpose in the paper-coating process is to cover the body paper, giving it an even surface, susceptible of a high and glossy finish. The glue used is of the ordinary sort so well known in the regular market. Its presence renders the clay solution very adhesive when applied to the body paper.
♦Extreme smoothness required♦
The cost of illustrations having been greatly reduced through the perfection of photogravure or half-tone processes, a large and increasing demand exists for a paper of extremely smooth, firm, and sensitive surface, suitable for the reproduction of the finest half-tone cuts; a paper with such delicate fineness and susceptibility that the minute lines of a photogravure cut—so minute in instances as to be indistinguishable to the touch of the finger—will be perfectly reproduced when printed upon its enameled surface.
Large factories are devoted entirely to the coating process. They do not necessarily make their own body paper, but frequently purchase it from outside sources. At first, this clay solution was carried to and spread upon the surface of paper by the use of a fine hair brush. This was applied to one side or surface of the paper at a time, the same process being repeated on the opposite side, if both were to be coated. Since its earlier introduction, the process of surface-coating paper has undergone great improvement, and the method to-day in vogue, while seemingly complete and exceedingly rapid, is yet readily understood, and the machinery required is quite simple. This consists of: