The maximum amount of expansion in the case of the vegetable fibres is obtained by gently breathing upon them rather than by the use of an excess of water.
These figures are important as explaining many of the peculiar characteristics of vegetable and animal fibres. Advantage is taken of the greater expansion of the latter in the manufacture of instruments for the measurement of moisture, such as the hair hygrometer, in which the elongation of a stretched hair registers the variation in the moisture of the atmosphere.
Quality of Book Papers.—The Committee of the Society of Arts in dealing with the evidence as to the permanence of finished papers suggest the following classification as indicating the desired standards of quality:—
(A) Classification as to Fibres.
A. Cotton, flax, and hemp.
B. Wood celluloses, (a) sulphite process, and (b) soda and sulphate process.
C. Esparto and straw celluloses.
D. Mechanical wood pulp.
The Committee find little fault with the Principles which govern the trade in the manufacture of high-class papers, and limit the result of their investigation to the suggestion of a normal standard of quality for book papers required in documents of importance according to the following schedule:—