The difference between these two papers, both consisting, as they do, of pure esparto with a small proportion of ash may be emphasised by comparing the analysis by weight with analysis by volume. The two papers in question when analysed by weight proved to have the following composition:—

—Parts by Weight.
Featherweight.Ordinary.
Esparto fibre96·095·4
Ash, etc4·04·6
————
100·0100·0

But if the papers are compared in terms of the composition by volume, it will be found that the featherweight contains a large amount of air space.

—Composition by Volume.
Featherweight.Ordinary.
Esparto fibre28·065·5
Ash, etc0·71·8
Air space71·332·7
——-——
100·0100·0

In other words, the conditions of manufacture for the bulky paper are such that the fibres are as far apart from one another as possible, and the cohesion of fibre to fibre is reduced to a minimum.

While paper of this description is agreeable to the printer, and probably to the general reading public, yet its strength and physical qualities, from the point of view of resistance to wear and tear, are of the lowest order. It is very difficult to rebind books made from it, which is not altogether to be wondered at, seeing that the bookbinder's stitches can hardly be expected to hold together sheets containing 60 to 70 per cent. of air space.

This concrete case emphasises the necessity for including in a schedule of standards of quality a classification of papers according to strength and bulk.

Surface.—The introduction of new methods of printing has brought about some changes in the process of glazing and finishing paper which are not altogether favourable to the manufacture of a sheet having maximum qualities of strength and elasticity, two conditions which are essential to permanence. In other words, the very high finish and surface imparted to paper by plate-glazing, supercalendering, water finish, and other devices of a similar character is carried to excess.

All papers are improved in strength by glazing up to a certain point, but over-glazing crushes the paper, renders it brittle and liable to crack. Unfortunately, the maximum strength of a paper is generally reached before the maximum of finish, with the result that the former is frequently sacrificed to the latter. The usual result of glazing is found in an increase of 8 to 10 per cent. in the tensile strength, but a diminution of elasticity to the extent of 8 to 10 per cent. With supercalendered magazine papers, the high surface is imparted for the sake of the illustrations which are produced by methods requiring it. The addition of considerable quantities of clay or mineral substances improves the finish, so that the question of the relation of glazing to strength, surface, and loading is one which affects the subject of deterioration of paper very materially. With writing paper the false standard of an “attractive” appearance is almost universally accepted by the public as the basis of purchase without any reference to actual quality.