530 FULLING 



a. By discovering new, and increasing the consumption of already used, 

 non-vegetable tanning agents 



b. By increasing the use of already utilized native American vegetable 

 sources other than chestnut wood, and by employing other native sources 

 not yet exploited 



c. By promoting domestic cultivation and harvesting of exotic tannin- 

 yielding plants 



Of the potential native sources, the most exploited so far is tanbark oak 

 bark of California, already referred to. Use of this bark has always been con- 

 fined to the few tanneries along the Pacific Coast, where it is usually blended 

 with quebracho. In California it is the principal source, but in the entire 

 national picture it constituted only 0.8 per cent of all domestic tannins in 

 1942. The trees, up to 80 feet in height, cover some three million acres in 

 California and southern Oregon. When cut, they sprout quickly from the 

 stumps, a second cutting is possible at the end of twenty years, and the wood 

 is suitable for conversion into paper pulp. Greater exploitation of this two- 

 product forest species has thus been advocated, envisioning a new 6-minion- 

 dollar annual economy for the state of California. Technological advances, 

 suitable economic conditions, and proper silvicultural practice may some day 

 render the tanbark oak an important arborescent replacement of South Ameri- 

 can quebracho as an industrial source of tannin. 



Other unused and waste tanniniferous native barks not fully exploited are 

 those of Florida scrub oak {Quercus laevis) with 10 per cent tannin; western 

 hemlock (Tsuga heterophylla) , 15 per cent; Douglas fir {Pseudotsuga taxi- 

 folia), 10 per cent; Florida mangrove (Rhizophora mangle), 31.5 per cent; 

 and a mixture of 15 Tennessee Valley oaks, averaging about 8 per cent 

 tannin. 



Other than the foregoing barks, the only commercially potential native 

 sources of vegetable tannin investigated so far have been canaigre root and 

 sumac leaves. 



Canaigre,'^ or tanner's dock {Rumcx hymcnoscpalus), is a polygonaceous 

 perennial herb, up to 3 feet in height with leaves up to 20 in. long, native 

 to the southwestern United States and northern Mexico, where the Indians 

 and Mexicans have long used the roots in preparing leather. The roots contain 

 10 to 35 per cent tannin and first came to the attention of the U.S. Depart- 

 ment of Agriculture in 1868. Not until ten years later, however, was an 

 analysis made of them, and the first recorded attempt to market the roots 

 on a commercial scale was in 1882; in 1886 a canaigre tannery was built in 

 Tucson, Arizona; the next year large-scale shipments of roots went to Scot- 



^ Corruption of the common Spanish name "cafia agria" (sour cane) in Me.xico. 

 Known there and in New Mexico also as "yerba colorada," or "red root," and in the 

 United States as "wild rhubarb." 



