The paper used in newspapers is nearly all made entirely of ground wood. Most of it is made as cheaply as possible, and soon grows brittle and dark in color. This is of little consequence in most cases. For the ordinary newspaper the paper has served its purpose if it looks well for twenty-four hours after it is printed and exposed to the light.
Books are generally printed on paper which has not been very highly polished. Ink is taken from the type more readily by paper of this kind, especially if the latter be rather soft in texture, so that the press drives into it the face of the type bearing the ink. Modern processes of reproducing pictures give plates for printing, many of which are made up of very fine lines placed very closely together and having very shallow depressions between them. To print from these with good results the paper used must have a very smooth, highly polished surface. The press drives soft paper down into the narrow places between the fine lines and blurs the impression of the cut. Newspapers which use process-cuts of the kind mentioned are obliged to use paper with a smooth surface to get good results. This smooth surface is generally produced, as already noted, by passing the paper between hot metal rollers, a process called calendering. In a more expensive process, called plating, the paper, cut into sheets, is laid between sheets of zinc until a pile of several inches in thickness is formed, and this pile is passed several times under rollers exerting a heavy pressure. This smooths, polishes and hardens the paper. Much of the paper used for illustrations in books has a surface made by applying a coating of clay or other material to it and then polishing it. Quite good results can be obtained with fine line cuts on calendered or plated paper without the addition of a coating of clay. The illustrations on coated paper which are found in books are very commonly printed separately from the book itself, which is on ordinary uncoated paper, and inserted separately. Generally these inserts are not carefully fastened in and cause much annoyance by falling out after the book has been subjected to a little use.
Recently paper makers have succeeded in producing a paper which has a smooth surface without the high polish usually found on that which is coated, or highly calendered. The polished surface of these papers, especially of the coated, is very objectionable to readers, light being reflected from it in an unpleasant way.
It will be seen from what has been said that it is difficult so to describe what we may call good book paper that it can be readily distinguished. Constant study and careful comparisons of the papers one meets in books will enable one to judge of them with some success. One who has much to do with books should take note of the paper of which they are made, and learn to distinguish between poor and good, and the good and the best, as far as possible. This is especially desirable for one whose work with books includes their rebinding and repairing. Coated paper breaks easily, the stiffening added to it by the coat of clay giving it a tendency to fall apart as soon as it has been folded in the same place a few times. Soft and fragile paper, such as is found in many books, will stand very little wear at the joint in the back. Paper not carefully bleached and freed from the chemicals used in bleaching, rapidly discolors at the edges where exposed to light. Such facts as these, and many others, will be found useful when one comes to have books rebound, or attempts to repair them.
That side of the paper which touched the wires on which it is made is different from the other. This difference is usually visible to the trained eye. It is often taken into consideration in fine printing.
As the pulp flows out upon the wires it tends to mat together more thoroughly along the line of flow than across it. This gives paper a grain, along which it tears and folds more readily than across it. This fact also is often taken advantage of in good printing.
All paper expands or stretches when wet. This is to be kept in mind in mending books. An added strip, pasted on, usually draws and wrinkles, when it dries, the paper to which it is applied. Hence the rule, in mending, to use thick paste and apply the pasted sheet or strip to its place as quickly after pasting as possible.
Mr. Chivers has recently made, 1909, with the help of chemists and other experts, a very careful examination of the composition, structure, tensile and folding strength and other qualities of the paper now used in several thousand popular books. The results of this examination, when applied to the subjects of book-selection and book-buying, will be of great value to libraries. The quality of the paper used in the books on which libraries spend a large per cent. of their book fund—novels—is the question that should be first considered in selecting editions. Libraries may hope soon to be able to select editions much more wisely than heretofore. The investigations by Mr. Chivers, and those carried on by U. S. Government experts in Washington, will not only enable libraries to discover the best editions for purchase, but will also enable them to secure bindings so carefully adapted to the quality of the paper in each book as to give that book the longest possible life of usefulness.