Page:Paper and Its Uses.djvu/47



manufacture of boards is varied, ranging from Bristol boards to millboards, and including ivory boards, pasteboards, triplex boards, strawboards, and pulp boards.

For pulp boards the description of papermaking will serve in its entirety, as the boards are made on the Fourdrinier, being engine-sized, reeled at the end of the machine, well rolled later, cut into sheets, sometimes plate-glazed after this, and then sorted and packed. There is one point of variation only, and that is in speed. As there is much more "stuff" let down to the wire, a greater thickness of material for the water to drain from demands more time, and so the output is relatively slower than when paper is being made.

For ivory boards, two or more sheets of fine paper made on a Fourdrinier, or else on a cylinder machine, are brought together at the couch rolls, and the sheets are pressed and rolled together without the use of paste.

Cylinder machines are invariably used for duplex, triplex, and boards of several layers other than paste boards and those already described. Instead of a travelling wire, a wire-covered cylinder is the means of forming the film of pulp. The cylinder revolves in a vat of pulp, takes up a thin layer of the fibre, and, pressing against a travelling felt, leaves its film of