CHAPTER I.
THE PUERING AND BATING PROCESS.
“Beizen sind Stoffe die mit dem Kalk nicht nur ein chemische Verbindung einzugehen im Stande sind, wodurch derselbe löslich und somit vollständig unschädlich wird, sondern auch den gegenseitigen festen Schluss der einzelnen Wandungen der Zellenelemente mechanisch lockern, den ganzen Bau der Haut in sich nachgiebiger machen und so die Verschiebbarkeit der einzelnen Hautgebilde erhöhen.”—J. C. H. Lietzmann, 1862.
“Bates are materials which are not only able to enter into chemical combinations with the lime, whereby it becomes soluble, and is thereby rendered completely harmless, but they also mechanically loosen the cementing substance of the separate cell elements, and render the whole structure of the hide more pliable, and thus increase the mobility of the various parts.”
The object of bating or puering is to render the skins, and the resulting leather, soft and supple. Skins which have undergone the liming process, must be thoroughly freed from lime before going into the tan liquors, and, for light and soft leathers, they must be reduced or “brought down,” so that the elasticity or resilience of the skin fibres is got rid of, and the skin, when tanned, can be stretched without springing back. This is usually done in the case of light leathers, by passing the skins through a bate or puer, composed of an infusion of dogs’ dung in water at a temperature of 35° to 40° C., until the required result is obtained. This condition is known to the workman by the feel of the skin. A good indication is, that the skin when “down” retains the impression of the thumb and finger if squeezed. A properly puered skin, when dropped on the floor, will also be perfectly flaccid, the folds lying closely together. It may, however, be said that it is only by experience and a kind of instinct that the exactly correct condition of the skin can be judged.
I know of no very early works on leather manufacture giving an account of bating. It was a “secret process,” and the results obtained depended almost entirely upon the judgment of the operator; and this judgment was frequently in error, owing to the fact that he did not understand what took place in the bate.
The earliest account I have been able to find is in a book[5] in the possession of Mr. Seymour-Jones, of Wrexham, entitled “The Art of Tanning and Currying Leather, with an Account of all the Different Processes made use of in Europe and Asia for Dying Leather Red and Yellow, Collected and Published at the Expense of the Dublin Society, to which are added Mr. Philippo’s Method of Dying the Turkey Leather as approved of by the Society for the Encouragement of Arts, etc., and for which he had a Reward of £100, and their Gold Medal, for the Secret. Also the New Method of Tanning invented by the late David Macbride, M.D., London. Reprinted for J. Nourse, on the Strand, Bookseller to His Majesty, 1780.”
In the chapter entitled “Alumed Calf Skins for Bookbinding” (p. 138), after the limed skins have been fleshed, the writer continues—
“To alum them, put into a large vat, three or four pails of dogs’ turd (this dogs’ turd is called alum); on this they fling a large pail of water to dilute it; this done, the workman goes into the vat, and, with his wooden shoes, tramples it, filling the vat half full of water. The alumer, on his part, pours water out of his boiler into this vat, mixing it with the cold water, after which he flings in the skins, stirring them and turning them for some moments with great sticks.”