Chemistry of Leather Manufacture

Tannin, or Tannic Acid (Vol. 26, p. 399) is a general account of the vegetable products which have the property of converting raw hide into leather. Specific information about the materials from which the pyrogallol tannins are obtained will be found under Myrobalans (Vol. 19, p. 114), Chestnut (Vol. 6, p. 112), Dividivi (Vol. 8, p. 332), Sumach (Vol. 26, p. 70), Oak (Vol. 19, p. 931), Galls (Vol. 11, p. 422) a full and interesting account of the insect produced vegetable excrescence which yields a high percentage of tannin, by Francis H. Butler, of the Royal School of Mines; and Willow (Vol. 28, p. 688). For the catechol tannins see Hemlock (Vol. 13, p. 262), Catechu (Vol. 5, p. 507), Mangrove (Vol. 17, p. 572), Mimosa (Vol. 18, p. 500), Larch (Vol. 16, p. 211), Birch (Vol. 3, p. 958), which yields the empyreumatic oil used in the preparation of Russia leather, to which the pleasant odor is due.

There are numerous articles in the Britannica on the chemicals used in the process of tawing, chrome tanning, etc., such as Alum (Vol. 1, p. 766), Acetic Acid (Vol. 1, p. 135), Glauber’s Salt (Vol. 12, p. 114), Bichromates and Chromates (Vol. 3, p. 912).

Dyeing

The chief classes of dyes used for leather are the acid; basic, or tannic; direct, or cotton; and mordant dyes, and these are described at great length in a valuable article Dyeing (Vol. 8, p. 744), equivalent to 20 pages of this Guide, by the late J. J. Hummel, professor of Dyeing, University of Leeds, and Dr. Edmund Knecht, professor of Technological Chemistry, University of Manchester. The section on the Theory of Dyeing shows how the dyeing property of a substance depends upon its chemical composition. Separate articles go more deeply into the chemistry of dyeing materials used with leather, and some of the more important of these are Sulphonic Acids (Vol. 26, p. 60), Sulphuric Acid (Vol. 26, p. 65), Formic Acid (Vol. 10, p. 668), Antimony (Vol. 2, p. 127), Titanium (Vol. 26, p. 1017), Iron (Vol. 14, p. 796), Logwood (Vol. 16, p. 922), Fustic (Vol. 11, p. 375), Brazil Wood (Vol. 4, p. 463), and Tumeric (Vol. 27, p. 474). Comparatively few of the coal-tar colours have as yet been adapted to leather manufacture, but their characteristics are discussed in such articles as Azo-Compounds (Vol. 3, p. 81), Aniline (Vol. 2, p. 47), Indulines (Vol. 14, p. 507), Fuchsine (Vol. 11, p. 273), and Safranine (Vol. 23, p. 1000).

Special Leathers

Parchment (Vol. 20, p. 798), by Sir E. Maunde Thompson, Principal Librarian, British Museum, is an interesting historical account of the skins and their preparation. Their use as writing material was widespread at a very early period. “The Jews made use of them,” says the article “for their sacred books, and it may be presumed for other literature also; and the old tradition has been maintained down to our own day, requiring the Synagogue rolls to be inscribed on this time-honoured material.” The difference between parchment and vellum is explained. Shagreen (Vol. 24, p. 769) tells about a species of untanned leather used for ornamental purposes. It is a curious fact that the addition of the word “chagrin,” for anxiety or annoyance, to the English language was due to the unpleasant sensation that came from touching the rasping surface of this leather. Stamped leather for wall hangings is described in the section Stamped Leather of the article Mural Decoration (Vol. 19, p. 19), by William Morris and Walter Crane. Shoe (Vol. 24, p. 992) contains an illustrated section on the Manufacture of Leather Shoes. Saddlery and Harness (Vol. 23, p. 988), by Cecil Weatherly, and Glove (Vol. 12, p. 135) are treated both from an historical and a practical point of view. Bookbinding (Vol. 4, p. 216), illustrated, by C. J. H. Davenport, of the British Museum, has a great deal of interesting information about the leathers used in this art. The flexible binding, which has been applied for the first time on a large scale in the new Britannica, originated when vellum instead of paper was used for books, and it possesses the great advantage that a volume sewed in this way can be opened flat, and lies flat without being held.

ALPHABETICAL LIST OF ARTICLES AND OF SUBJECTS IN THE ENCYCLOPAEDIA BRITANNICA OF SPECIAL INTEREST TO THOSE IN THE MANUFACTURE AND SALE OF LEATHER AND LEATHER GOODS

CHAPTER X
FOR JEWELLERS, CLOCK AND WATCH MAKERS AND MERCHANTS