Paper and Its Uses/Chapter 10
CHAPTER X
MISCELLANEOUS PAPERS
Blotting, Duplicating, Copying, Tissue, Cover,
Gummed, Wrapping
There are so many varieties of paper which are only occasionally encountered that it is better to present the whole of them in alphabetical arrangement (see Chapter XVII.), and in this section to give a longer description of a few representative papers.
Blottings and filter papers are very similar in appearance and manufacture, their definite purposes being to absorb moisture, and to filter suspended matter from solutions respectively. The description of blotting paper manufacture will cover both varieties. The office of blotting paper being to absorb ink, the raw material is chosen with a view to obtain the most efficient fibre for the purpose, soft muslins, too soft for writing papers, making excellent blottings. The preliminary treatment of the rags has been described already. Beating is carried out as quickly as possible, sharp knives being used to cut the fibres into short lengths, and not to bruise or beat the fibres more finely. As many fibre ends as possible must be absorbing on a given area at one time, and the shorter the lengths to which the fibres are cut, the greater the efficiency of the blotting paper, within certain limits. Certain after-treatment of the fibre is resorted to, to produce as soft and absorbent a fibre as is consistent with the necessary cohesion, but of course manufacturers prefer to keep special methods to themselves. At the paper machine little or no shake is given, and very light pressure is given throughout, just sufficient to smooth the paper down. Strength is not aimed at, but the paper must be strong enough to resist the handling it will receive in ordinary use.
Most blotting papers are made in demy, with a standard weight of 38 Ib. per ream of 480 sheets. There are blottings made of wood pulp, but these are far below the rag papers in efficiency. Soda wood pulp makes a very fair blotting paper, but sulphite wood is not so absorbent as soda pulp paper. Wood pulp blottings are usually made in thin substances for interleaving diaries and similar books, where repeated use will not be required. Enamelled blotting papers are made by pasting enamelled (coated) papers to the ordinary blotting paper and rolling down. These blottings can be obtained in a variety of colours, both the blotting and surface paper being varied in colour. Coloured blottings are made of the usual ingredients, with added colouring matter.
Duplicating, impression, and multi-copying are different names for the same papers. They are used for the various duplicating machines of the cyclostyle and mimeograph patterns, where a number of copies of written or typewritten matter is required quickly. A very thin ink is used, and it is necessary that it should be absorbed very speedily. These papers are practically unsized, contain a large proportion of esparto for the better qualities, and a certain quantity of mechanical wood in the cheaper sorts. A very large range of these papers is obtainable: laid or wove, white, cream or tinted, with rough or moderately smooth finish. For copies produced by the same process, where a signature has to be appended, or when the form serves as a blank for written additions, a half-sized paper is obtainable in similar qualities and tints.
Tissue papers are strong, thin papers, the best quality being made from hemp or rag fibre, well beaten, with no loading or sizing, made in blue or cream, usually double crown in size; other qualities are made from mixtures of rag, chemical wood, and straw, in various proportions and in various weights. Tissues serve a large number of purposes, as wrappings for high-class goods, therefore they must be strong and free from chemicals, for fly-leaves for the protection of engravings and prints, and also for the basis of carbon papers which are used for obtaining a simultaneous copy of written or typewritten documents.
Copying papers are similar in all respects to tissues, but some varieties have a small amount of mineral matter added to increase their efficiency. Made in cream wove, blue wove, and buff, put up in reams of 500 sheets, copying papers are used for press copying correspondence which has been made in copyable ink. Special typewriter ribbons are supplied, but most typewritten matter copies without trouble. The leaf of the copying book is damped, the excess of moisture removed by an absorbent sheet, the document inserted, the book closed, and pressed in the copying press. By this means copies of orrespondence are preserved for reference. Copying paper is also made up in rolls for copying machines which carry out the damping and copying automatically.
Cover papers are obtainable in many qualities, colours, and sizes. The materials used in their manufacture run through the whole range of papermaking fibres, the best qualities having a good proportion of rag fibre, while the low grades have some quantity of mechanical wood, but there should be little if any mineral matter present, as strength is an important feature. The finish of the papers is smooth, moderately rough, or rough; the colours tend to browns, greys, slates, and dark greens, but a fair number of more delicate shades can be obtained, and some of the reds are most effective. The substances of cover papers run from 18 Ib. to 56 Ib. demy per ream of 480 sheets, so there is sufficient variety from which to select paper to suit any job.
As covers for booklets, price lists, pamphlets, etc., cover papers are regularly used, and for other purposes there has arisen a demand for the darker shades. The army of photographers, professional and amateur, have employed cover papers as mounts, either in the form of cut mounts or as photographic albums. For these purposes the range of substances has been extended, the heavy papers being made in card thicknesses. In making papers for photographic mounts a very necessary quality is that the paper shall be absolutely free from chemical substances likely to affect the photographic prints mounted upon them. Colour prints are mounted on neutral cover papers for insertion in magazines or books, but when publications have extensive and growing circulations, the time and cost of mounting militate against this very effective method of displaying illustrations.
Embossed cover papers are made and finished in the usual manner, and run through special rolls having the pattern engraved upon them. Papers for embossing must possess good strength or the embossed design will not stand handling, or the paper may break when embossed.
Pamphlet cover papers are thick tinted papers, made in a very pleasing variety, serving as programme papers and for much jobbing work, as well as for the purpose for which they were originally intended.
Covers for exercise books are usually glazed on one side only (M.G.). This should be the outside of the book, and any printing should be executed on the smooth side. "Pressings" are the papers usually employed for such purposes, a cheap cover paper obtainable in various colours, weights, and sizes.
Gummed papers are made in a variety of qualities, colours, and substances. The papers range from the thinnest printing to thick enamelled paper, and the thickness of the coating of gum is varied to meet all requirements. Many colours of paper can be procured ready gummed. To obtain a satisfactory gummed paper three things have to be studied: body paper, gum, and thickness of coating. The inherent fault of gummed papers is the tendency to curl, but the extensive manufacture of non-curling gummed papers has done much to remove this bugbear. By adopting a paper which is affected but little by atmospheric changes something is accomplished in the minimising of curling, but by an ingenious breaking of the gummed surface non-curling is secured. When the coating is dry, the paper is drawn over a steel edge to break the homogeneous film of gum into innumerable fragments. In absorbing or parting with moisture (the cause of curling) the small particles can only act as individuals instead of combining and curling. Any kind of paper can be gummed, but the thinner the paper the more effective its adhesion when used as a label. When a label, slip, or any printed matter has to cover other printed matter, the paper must be thicker and opaque enough to prevent the matter beneath from showing through.
Wrapping papers are of many kinds, of various substances and colours, and are varied, too, in surface. The materials used range from the strongest to the weakest—from hemp rope to mechanical wood and include jute in the form of old gunny bags or sacking, hemp refuse, old rope and string, waste card cuttings, old paper, and wood pulp refuse. The substance ranges from 38 Ib. to 160 Ib. per ream of 480 sheets in double imperial, the colour from "white" to a very dark brown, and the finish from highly glazed both sides to a rough air-dried surface.
Strong materials are boiled under pressure for several hours, lime being employed for hard papers, and soda for softer papers. The fibres receive but little washing, going on to the beaters, where the stronger fibres are first reduced and the softer materials added later. Loading, colouring, and size are added, and the paper made on the Fourdrinier. Air-dried browns are specially tough, very leathery, will stand a great deal of folding, and when packing and unpacking of parcels is required the extra cost is easily recouped. Cylinder-dried browns are dried on the paper machine, and the papers are not so elastic as air-dried papers of the same substance. Glazed browns are usually lighter in colour and cleaner in appearance than the ordinary wrappings, and usually contain a large proportion of wood pulp. Kraft browns may be described as glazed browns, as they are sometimes finished with a glazed surface both sides. A special kind of pulp is used for krafts, wood being digested at a comparatively low pressure with soda solution, the boiling being prolonged. The fibres are loosened, and reduction to pulp takes place in the edge runner (kollergang) instead of the beating engine. By this means the fibres are drawn out, not cut up, and very tough papers can be made, fully entitling the papers to their description as "kraft" (German for "strength"). Special wrappings which will not discolour the goods packed in them are necessary for packing such fabrics as cotton goods, this quality being made without added colouring matter. Ream wrappers are sometimes thick common papers, serving as protective coverings only, being heavy but with little strength. Some papers are packed conscientiously, the manufacturer or stationer recognising the fact that a valuable paper demands a good packing paper. The use of poor paper is strange, seeing that the printer is charged for the wrapper at the rate quoted for the contents.