78 FOREST PRODUCTS 



the season usually runs from May to August of each year. The process 

 follows along the same general plan of that described for eastern hemlock. 

 There are several difiiculties, however, in harvesting western hemlock 

 bark which do not occur in the eastern states. The timber, being of 

 much larger size, presents difficulties in getting out the bark, and loggers 

 who operate largely with steam logging devices do not care to bother 

 with bark as a by-product. Owing to the very rainy climate, the bark 

 seasons out with some difficulty. It is handled, treated, and used in the 

 same way as the eastern hemlock. 



There are no accurate statistics of the present annual production of 

 western hemlock bark, but it has been estimated that it supplies about 

 two-thirds of the present annual requirements of the tanneries in the 

 northwest. With the further development of that rapidly growing sec- 

 tion, and the installation of more and larger tanneries, it is believed 

 western hemlock will assume greater importance as a source of tanning 

 materials. 



BLACK OAK BARK AND OTHER DOMESTIC MATERIALS 



Black oak (Quercus velutina) or yellow oak has recently come into 

 some prominence a? a source of tanning materials, especially by the manu- 

 facture of a certain extract which is called " Quercitron." Its center of 

 production is in Pennsylvania and the southern Appalachians. These 

 trees yield a fairly thick bark, and have a tannin content of from 6 to 

 12 per cent. It is produced in the same manner as has been described 

 for the bark of the chestnut oak. Its principal drawback is that it 

 mildews rather easily and care must be exercised, therefore, in the drying 

 process and in stacking in the woods. Leather made from it has a violent 

 yellow color. The price ranges somewhat below that for chestnut oak. 

 In West Virginia in 1910 it brought the high figure of $10.30 per cord 

 f.o.b. cars. Since then its. price has risen still higher on account of the 

 demand for tanning materials during the war. There are no figures 

 available as to the total output, but it is relatively small as compared to 

 other barks. 



Other barks and materials produced in the United States are as follows: 



White oak bark is used to a limited extent in the eastern and south- 

 eastern states. Its tannin content is from 4 to 7 per cent. The bark is 

 rather thin, however, and it is not believed that its use will increase 

 very much in the future. 



Sumach leaves, when dry contain a large percentage of tannin ; from 

 10 to 25 per cent. There are two tannin producing varieties of native 



