SOURCES OF TANNING MATERIALS Conifers.
Hemlock (Duca Canadensis). Hemlock bark is still the chief American tanning material. It contains 8 to 14 per cent of catechol tannin. The tree is native from Nova Scotia to Minnesota and Wisconsin, and southward in the Alleghany mountains to Northern Alabama and Georgia. Michigan and Pennsylvania furnish about 60 per cent of ali the hemlock bark now secured. The bark is used extensively alone or in combination with oak hark in the production of sole leather. Hemlock leather is harder and less pliable but more permeable to water than oak leather. The total quantity of hemlock bark used in 1905 was 1,000,000 cords, worth $8,470,000. An extract is also made of which about 52,000 barrels were used in 1905.
Western hemlock (Taiga heterophylla) is found from Alaska to Idaho and Montana, and southward in the Cascade and Coast ranges of Washington, Oregon and California, where it may constitute 13 per cent of the forest growth. The bark contains 8 to 20 per cent of tannin and is somewhat thinner than that of eastern hem lock. The wood contains less than one per cent of tannin.
California swamp pine (Pines muricata) is native along the coast of upper and lower California. The bark con tains about 13 per cent of tannin.
Monterey pine (Pious radiate) is native on the coast of California. The bark contains about 14 per cent of tannin.
Pine bark is used largely in Austria, Bavaria and southern Germany. Aleppo pine (Pines Halepensis) con tains about 15 per cent of tannin very similar to hemlock. The inner part of the hark is called Snoubar and contains as much as 25 per cent of tannin of lighter color than the outer bark. Other pine barks contain 2 to 7 per cent of tannin.
Silks spruce (Picea Sitchensis) is native along the coast from Alaska to northern California. The bark contains about 17 per cent of tannin.
Norway spruce (Picea excelsa). The bark contains 7 to 13 per cent of catechol tannin and much fermentable sugar. It is used largely in Austria and is the source of the so-called larch bark extract. White spruce (P. alba), native
in northern United States and Canada, is very similar.
Silver fir (Abies pectinata) is used to a limited extent. The bark contains 6 to 15 per cent of iron-bluing tannin.
Lowland fir (.4bies grandis) is native along the coast from Vancouver island to northern California, and inland to Idaho and Montana. The bark contains about 9 per cent of tannin.
Larch (Larix Europma) contains 9 to 10 per cent of a pale catechol tannin and is suitable for light leathers.
Dwarf juniper (Juniperus communis) bark is used in Russia. Several members of the Taxaceae or yews are used in Australasia for tanning and contain 20 to 30 per cent of tannin.
Redwood (Sequoia sempervirens) is native along the coast and thirty miles inland from southern Oregon to south of Punta Gorda, California. The wood contains about 2 per cent of tannin and the bark probably some what more.
Big tree (Sequoia gigantea) produces a gum which exudes from the tree and which may contain as high as 70 per cent of tannin.
The oak tannins.
Chesnut oak (Quercus Prima) is found from southern Maine to Maryland and in the mountains southward to northern Alabama and Georgia, and westward to Lake Erie and central Kentucky and Tennessee. Chestnut oak bark is next in importance to hemlock bark in this country, and contains 8 to 14 per cent of tannin, probably both catechol and pyrogallol. The wood contains 2 to 5 per cent of tannin. An extract is also made from the bark. It is customary to cut all trees when the sap is rising if the bark is to be used, as it can be most easily peeled at this time. All barks should be carefully piled in the woods as peeled, as otherwise there is considerable loss of tannin from exposure to the weather. The quantity of oak bark used in 1905 was 422,000 cords, valued at $3.765,000 ; in addition, 214,000 barrels of extract, valued at $2,300,000, Was also used.