Paper Manufacture

If this were not the Electrical or Nuclear Age, it would certainly deserve to be remembered as the Paper Age, for never has so much paper been used or printed upon, by so many people or for so many purposes. Paper making is a fairly complex process and involves the use of machines which include a wide variety of rollers, wheels, semi-liquid pumps and wire gauze, all comprising a proportion of copper alloys.

Good papers are made from rags, straw, grasses, etc., and newsprint from pulpwood trees. The principal method of making paper by machine is worth outlining. First, the raw material is 'digested' in vats, i.e. it is cleaned, bleached and softened in an acid solution. The digester is equipped with copper or brass cooling pipes, while the evaporation of the surplus liquor involves copper evaporator tubes and sometimes copper cylinder - applications where copper is chosen for its high thermal conductivity. The bleached stock, a thick semi-fluid mass, is pumped into beaters, where the fibres are chopped up and shredded and the whole is reduced to an even consistency. This is the most important operation in paper making. The beater comprises a large revolving roll or cone, in stone, steel or bronze, into which are set numerous sharp-edged, flat-ended beater bars; these oppose similar bars set in a baseplate. A beater roll may be 5 ft. in diameter, and weigh 10 tons or more with up to 160 bars. Normally the beater bars are made of 94/6 tin bronze; but aluminium bronze and other alloys are also used. On leaving the beater trough the paper material is an even pulp. It is pumped into feeeding tanks, from which it is spread over the surface of a rapidly moving endless wire cloth screen, 40 to 60 mesh, or occasionally even finer. This screen, known as the Fourdrinier wire, is a weave of brass or copper rollers. In one giant machine, the screen is 26 ft 8 in. wide and 100 ft. long. As the pulp passes along, surplus moisture is drawn out from below by suction, and the screen is a small wire-covered hollow cyliner called a dandy-roll, which smooths the upper surface of the pulp and at the same time impresses a watermark into it if required. The product now resembles wet paper. It passes over a very large perforated suction roll, then between heavy pressing rolls, and next through smoothing rolls, the lower of which is usually made of bronze or gunmetal. Finally, it traverses a vertical stack of rolls, commonly five in number, where it is calendered or given its surface finish. The paper is then would into rolls.

Plunger, vacuum or centrifugal pumps are necessary to handle the fluid stock and these include a large number of copper alloy components, as do the vacuum boxes.