Page:The American Cyclopædia (1879) Volume X.djvu/278

 272 LEATHER The importations of hides at London are not more than one fourth as large as those at Liver- pool, hut in hoth places there is a considerable business in "market" hides, as those from domestic cattle are called. The most impor- tant hide market on the continent of Europe is Antwerp. A summary statement of the trade there for the five years ending with 1873 shows the business in South American hides to have been as follows : Imports. Exports. Imports. Exports. 1869... 1870... 1871... 925,838 1,188,222 1,068,223 280,182 285,074 277,897 1872.. 1878.. 1,181.418 1,523,981 280,619 421,792 The difference between the exports and imports shows the number of hides, nearly all for the manufacture of heavy leather, which are sup- plied from this port for the use of German tanners. The calf skins used by the French and German tanners are nearly all furnished from domestic stock ; as a rule, all animals are better cared for there than here, and the skins are more carefully taken off, whicb. affords a partial explanation of the superior quality of French and German finished calf skins. Tan- ning Materials. Tannic acid is found in almost every plant which grows, and its use in making leather dates back as far as we have any rec- ords, and is attested in every sample of ancient leather extant. Among the sources of tannic acid, oak bark has the first place, although in the United States the bark of the hemlock is used even more than that of oak. Hemlock bark makes red leather, because of an excess of coloring matter, from which oak bark is com- paratively free. Oak-tanned leather always brings a higher price than hemlock-tanned, be- cause the coloring matter and resin which are to some extent imparted to the latter have a tendency to make it harder and more brittle, and also because of a prejudice against the red color, pure oak leather being often nearly white; but these points are not of so much importance as the fact that, because oak bark costs more, greater care is taken in the selec- tion of the hides and the finishing of the leather. As for the astringent principle of the bark, which unites with the gelatine and fibrine of the hide to constitute leather, there is no difference between that in oak and that in hemlock bark. The same cannot be said of all tanning substances, for chemists have not yet very closely defined what tannic acid is ; and while leather tanned with terra japonica, and some other kinds of concentrated tanning materials, may be restored to a condition very similar to that of raw hide, this cannot be done with bark-tanned leather. To make an accurate analysis of the amount of tannic acid in any given substance is one of the most difficult of chemical experiments ; and the re- sults of analyses made by different individuals, and even by the most celebrated chemists, vary so widely that the best informed tanners place no dependence on the figures thus given. The following table embraces all the principal tan- ning agents now in use, and is arranged with especial reference to the characteristic qualities that each is conceded to have in the leather manufacture; that is, those coming first in the list, before oak bark, make soft, open, mel- low leather, and those which follow oak bark make leather more plump, hard, and brittle. The figures given as showing the percentage of tanning cover only the variations found in excellent samples of the same material : TRADE NAME. Per- centage of tannin. Characteristics. Terra japonica. 42 to 50 Color bad; makes little weight; leather soft and open. Sumach 24 to 33 Color light; gives some firmness; makes leather soft and pliable. Myrabolams. . 28 to 44 Color yellow; makes little weight; leather mellow. Oak bark Hemlock bark. 11 to 13 11 to 18 Nearly colorless ; gives good weight ; makes leather very firm and solid. Color red; gives good weight; makes leather firm and hard. Yalonia 84 to 40 Color fair; gives weight; makes leather hard. Dividivi 26 to 50 Color poor ; gives great weight. Mimosa bark. . 24 to 36 Color very red ; gives weight ; makes leather hard and brittle. Of the above named tanning materials, a com- paratively small amount is used in the Ameri- can leather manufacture of any except oak and hemlock bark, and sumach, which is used prin- cipally in the tanning of goat skins. Hemlock bark is generally found north of the central portion of Pennsylvania, while south of that latitude most of the oak bark is used. In the northwestern counties of Pennsylvania, the northern counties of New York, W. and N". of Lake Michigan, and in Maine and Canada, are now found the principal hemlock forests, which it is estimated will furnish ample tanning mate- rials for at least 50 years to come. Along the Cumberland and Alleghany mountains, and all the lesser ranges of the Blue Ridge through the southern states, are large supplies of oak bark. Maryland and Virginia since 1865 have fur- nished a large amount of sumach, which, how- ever, is not so highly esteemed as that grown in Sicily, whence* considerable importations are made annually. Besides the bark used di- rectly for tanning at or near the localities where it is peeled from the tree, no inconsid- erable amount is used in the United States and Canada for the manufacture of bark extract. This is a process of leaching the bark and then evaporating the principal portion of the water, so that a concentrated solution of tan- nin is made, which may easily be shipped to distant tanneries; and much of this extract has found a ready market in England within the past five years. It has been a favorite idea with some who are well informed in the busi- ness that this trade will ultimately be very large, as oak bark costs in England from 6 to 7 a ton, and the cost of the extract delivered there is only about half as great; but prac-