[CHAPTER VI]
BROWN PAPERS AND BOARDS
Common Browns.—The raw material used in the manufacture of common brown papers is chiefly jute and waste fibres of every description, such as waste cuttings from boxboard factories, old papers, wood pulp refuse, and other substances of a like nature. The jute, in the form of sacking or old gunny bags, and the hemp refuse, in the shape of old rope and string, are subjected to a slight chemical treatment just sufficient to isolate the fibres to a condition in which it is possible to work them up into paper. The bagging and string are cut up in a rag chopper and boiled in revolving boilers with lime or caustic soda for several hours at a pressure of 20-30 lbs., the lime being used when it is desired to manufacture a harsh paper, and the caustic soda being employed for the production of paper having a softer feel. The pulp is not always washed very completely after the process of digestion, as is the case with white papers, and it is often possible to extract from brown papers of this class a considerable proportion of the alkaline matter which has not been thoroughly removed from the boiled pulp. The presence of this alkaline residue does not affect the quality of ordinary brown paper, but is frequently a serious defect in the case of middles or straw boards, which are afterwards utilised for boxes and covered with coloured papers. The colour of the paper pasted on to such incompletely washed boards is frequently spoilt by the action of the alkali when moistened with the paste used, many aniline dyes being susceptible to the small proportion of alkali present.
The stronger materials, such as jute or old rope and string, are either used by themselves or blended with inferior raw material according to the quality of the paper being made. The jute and hemp fibres are generally beaten by themselves in the engine before the other materials are added. The pulp is mixed with the required amount of loading, while the sizing and colouring operations are carried out in the usual way.
The common brown papers are known by a variety of trade names which at one time indicated the nature of the fibrous constituent, but at the present day the name is no guide or indication of the material used for the manufacture of the paper. The common heavy brown used for wrapping sugar and sundry groceries made in heavy grey and blue shades is a coarse paper made from cheap materials and containing a large proportion of mineral matter. It is usually supplied under the trade name of royal.
A somewhat lighter and stronger wrapping paper of a white or buff colour, used for wrapping groceries, tea, and cotton goods, is that known as casings, a name probably derived from the application of this paper originally to the lining of cases.
Manila papers so called were originally made from rope, but the term is now applied to papers which may be made entirely of wood pulp.
Rope browns are common papers made of fairly strong material of a miscellaneous character, this name having been derived from the fact that rope and similar fibre were at one time used exclusively.
Wood Pulp Wrappers.—Most of the papers of the present day are made from wood pulp, this material giving a thin, light, tough paper, which is pleasant to handle and forms a great contrast to the dense, opaque, heavily loaded, and inartistic specimens produced some years ago. Paper of this kind, though apparently more expensive than common browns, is really more economical in use. The paper is not only stronger, but it is possible to obtain a larger number of sheets for a given weight. The great advantage in the improvement of brown papers dates from the introduction of the now well-known kraft papers, which are of comparatively recent origin.