♦Parts of coating machine♦
First—A vat, to hold the enameling solution.
Second—Rollers, to regulate its distribution upon the web of paper.
Third—Brushes, to work out small lumpy particles and overcome any tendency to unevenness of coating.
Fourth—An automatic carrier, to convey the coated web through a drying-room; after which it is calendered to the surface wanted and cut into sizes required.
A roll of body paper ready to be enameled is placed before the vat which contains the coating solution. The end of the paper-web is started through the solution by being passed under a wooden roller hung in the vat—the purpose of the roller is to insure an even tension and uniform immersion of the web. After passing under the roller the paper-web leaves the vat, and is passed between two rollers that regulate the thickness of the coating and remove all surplus. From the rollers the web passes forward through two sets of brushes, one above and one below, both sets working back and forth transversely upon the top and bottom of the coated web. ♦Distribution of coating♦ Each set of brushes is comprised, first, of a coarse, then intermediate, and finally of extremely delicate brushes, made usually of camel’s hair, which as they play upon the coated surface work out all roughness or small lumpy particles, and reduce the coating to uniform fineness. ♦Carrier♦ Upon leaving the brushes, the paper reaches an automatic carrier. This consists of wooden slats conveyed at intervals upon two endless chains that pass at either side of the machine just outside of the coated web, the chains supporting the slats at their ends. As the paper reaches the slats it falls upon one, which by an ingenious device is carried forward and upward, permitting the coated web of damp paper to fall in long loops or folds—succeeding slats follow upon the carrier at regular intervals, and prevent any marring of the damp surface by keeping it from foreign contact. The slats upon the carrier convey the web in this festooned form through a drying-room, kept at a temperature of about 140° Fahrenheit, thus thoroughly drying the coated web. The paper, dried by its passage through the drying-room, is rerolled upon reels, and is then finished by being passed rapidly between alternate steel and paper rollers, after the ordinary method of calendering paper. ♦The gloss or finish♦ The rollers are susceptible to regulation or adjustment, so that almost any degree of gloss can be put upon the coated surface; hence, for the highest finished paper the rolls are set slightly closer together, giving greater pressure; and if necessary, the web can be run through a second or third time. After calendering, the paper is cut to sizes required, this being done in the same manner all rolled paper is cut into sheets, except that if three or four rolls are run through the cutter at once—as is frequently the case to facilitate rapid cutting—a device is used that causes the sheets from each roll to fall in separate piles, so that all of the sheets in each pile will be from one roll, insuring uniformity.
THE SUPERCALENDERS—[Page 82]
The quality and value of coated paper depend upon the quality of the body paper, the fineness of the clay and other ingredients used in the coating, together with the perfection of its manufacture.
♦Glazing processes♦