Many hides are not only salted but also dried in order to preserve them. Not much detail has been published with regard to the methods used, which no doubt vary much in different places, but probably in some cases the hides are salted in pile and in others by brining, and then hung up to dry. The principal object of this drying is to economise weight and cost of transport, but it makes the hides much more difficult to wash and soften for tanning, and probably the crystallisation of the salt has a weakening effect on the fibre. Hides cured in this way are styled “dry salted.”
A large number of the hides of the small native cattle of India are imported into this country in a dry-salted condition. The following particulars of their cure are taken from a paper by the Author and Mr. W. Towse.[16]
[16] Journ. Soc. Ch. Ind., 1895, p. 1025.
Dry-salted, or, as they are commonly called “plaster cures,” such as those of Dacca and Mehapore, are thickly coated with a white material, which in the first instance is merely the insoluble portion of a saline earth used in the cure; though in many cases it is applied in larger quantities than necessary, with the simple object of giving weight. The salting is thus described by Mr. W. G. Evans, who some years since had considerable experience as a tanner at Cawnpore:—
“The salt used by the natives is a salt-earth; and is so called by them. It is found extensively in the districts of Cawnpore, Agra, Delhi, Lucknow, Patna, etc., and has no doubt something to do with the localisation of the hide-curing and kindred industries in these places. The mode of procedure used is pretty much as follows:—the salt-earth is mixed into a very thin paste, and this is lightly brushed on to the flesh side one day, and the hide allowed to remain over night under cover. Next day, for best hides, the same solution is again spread on the flesh side of the outstretched hide and rubbed into it with a porous brick, and then for legitimate salting, the hide is allowed to dry under cover. If for export, the saltings may be three or four, and the hides are treated out in the open, subject to the intense heat of the sun; which accounts for the number of hides which go back in the soaks in England and elsewhere.”
“We had a clause in our agreement with hide-factors, that any hides which did not come down to natural suppleness in two days in clean water were to be returned. Of arsenic curing I know nothing, and it is not so much in vogue as formerly. There is quite a trade in Cawnpore, Lucknow, Allahabad, etc., in treating old and inferior hides with new for export, and great efforts are made by native holders to get their stocks down before the rains commence, as they say, and rightly I think, that hides are not worth so much after the rains by 30 per cent. The peculiar latent moisture of the rains affects them very detrimentally.”
Under certain circumstances this mode of cure gives rise to extensive iron-staining of the skins, and analyses of the material scraped off Dacca and Mehapore kips were undertaken with a view to elucidating the causes of this injury. The following are the results of the analyses referred to, which were made upon the residue after the rather considerable quantity of fibrous organic matter, which had been scraped off with the cure, had been destroyed by ignition, together no doubt with traces of ammoniacal salts:—
| — | Dacca. Entire Cure. | Mehapore. Entire Cure. | ||
|---|---|---|---|---|
| Sand and silica | 20·55 | 27·38 | ||
| Fe2O3 | 2·77 | 1·86 | ||
| Al2O3 | 2·48 | 2·74 | ||
| Mn3O4 | 0·60 | 0·40 | ||
| CaO | 2·60 | 3·70 | ||
| MgO | 3·38 | 3·69 | ||
| Na2O | 28·97 | 26·80 | ||
| SO3 | 38·90 | 33·75 | ||
| Cl | 0·22 | 0·18 | ||
| H3PO4 and CO2 | Traces | Traces | ||
| 100·47 | 100·50 |
The soluble salts of the Dacca cure were also analysed separately with the following result:—
| CaO | 0·70 |
| MgO | 0·60 |
| Na2O | 29·00 |
| SO3 | 37·90 |
| Cl | ·22 |
| Insoluble | 32·12 |
| 100·54 |