CHAPTER XII
DURABILITY OF PAPER
Paper is used for many publications and jobs of an ephemeral character, and for these the permanence of paper is never in question. On the other hand, ledgers, leases, agreements, share certificates, must be upon paper which is to all intents and purposes permanent and capable of resisting a good deal of handling. Printed records, too, must be preserved on paper that will, with ordinary care, be indestructible.
The constituents of paper, as shown in the first chapter, are vegetable fibres, mineral filling, colouring matter, and vegetable or animal sizing. The fibres producing the paper which approximates most nearly to a pure cellulose material, with the minimum of chemical and mechanical treatment, are, of course, the best possible. Classified with that in view, cotton, flax, hemp, chemical wood, esparto, and mechanical wood is the order of merit. Cotton is, more than any other material, the ideal fibre. It contains 91 per cent, of pure cellulose, has a comparatively small amount of incrusting matter, and its fibre is easily bleached, and easily prepared for papermaking. Consisting as it does of seed-hairs, cotton is a free fibre from the first. It consists of a long tube, of dumb-bell section, with a tendency to twist upon itself. Prolonged beating produces numerous fibrillæ, and the softness of the original fibre is preserved until over-beating is reached.
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