CHAPTER III.
PRACTICAL HINTS ON TANNING.

The Hon. Zadock Pratt, one of the largest Tanners in the State of New York, has given some very valuable information concerning the various tanning processes which his experience and knowledge have afforded him. We shall select a few of the most important as furnished by him to Morfit’s valuable work.

Skins with the hair on are first soaked in cold water for forty-eight hours, and are then subjected to the action of the machine (Monier & Ray’s Mill) for an hour and a half; exposure for which time is generally sufficient to render them pliable. Eight or ten skins, according to their size and thickness, are generally contained in the apparatus. The water is then allowed to drain off, a sufficient quantity of cream of lime is poured in and the skins are again beaten for four hours, when they are taken out and piled up. After having been left to drain for five hours in this position, they are again fulled for a time in the machine, and then are deprived of their hair and fleshed by the workmen. They are then beaten for an hour and a half in the machine, and cleaned and scraped with the slate. In order to remove the lime, some of which remains attached to the skins, they are now soaked in water containing one hundredth part of sulphuric acid, and, after being constantly stirred in this liquid for an hour, are washed and rinsed in running water.

This method of preparing skins for tanning dispenses with the laborious manipulations to which they are commonly subjected, and preserves their quality, not injured as they are in the old way, by the hands of the workmen. It also presents the additional advantage, that they do not require the long exposure to the action of lime which is so apt to injure their tissue.

Since I first commenced business, the gain of weight in converting hides into leather, has been increased nearly 50 per cent. That is, from a quarter to a third more leather can now be obtained from a given quantity of hides, than at the time when I learned my trade at my father’s tannery, conducted in the old fashioned way, some forty years ago. The great improvement in weight seems to have been gained by the judicious use of strong liquors, or “ooze,” obtained from finely ground bark, and by skilful tanning.

The loss and wastage upon hides, from hair, flesh, &c., may be estimated at from 12 to 15 per cent.

To green hides, particularly, nothing can be more injurious than to suffer them to remain too long in weak ooze. On the other hand, however, the effects of an early application of ooze, that is too strong and too warm, to green hides, is very injurious. It contracts the surface fibres of the skin, tanning at once the external layers so “dead,” as it is termed, as to shut up the pores, and prevent the tannin from penetrating the interior. In the impossibility of adapting fixed rules to the innumerable variety of cases, nothing can be depended upon but the judgment of the practical tanner. In softening hides, and preparing them for the process of tanning, a great deal depends upon the judgment of the one superintending the operation.

In “sweating,” the character of the hides, and the temperature, are essential, but ever-varying considerations. As a general rule, however, the milder the process for preparing the hides for the bark, the better. Too high a temperature is particularly to be avoided. Hides that are very stiff and hard, resisting all the ordinary modes of softening, are assisted by a solution of ashes, potash, or even common salt will be found beneficial; and particularly so in hot weather.

The following table may be found useful in conveying an approximation to a definite idea of the practice in my tannery:

Soaking.40°
Days.		50°
Days.		60°
Days.		70°
Days.
Buenos Ayres hides10 to 128 to 126 to 83 to 6.
Carthagena and Laguaira8 to 127 to 95 to 72 to 3.
Sweating.
Buenos Ayres hides15 to 2012 to 168 to 122 to 3.
Carthagena and Laguaira15 to 2010 to 156 to 82 to 3.