18 



CALIFORNIA TANBARK OAK. 



TABLE 8. Amount of bark on second-growth tan oak, age 29 to 31 years, Santa Cruz 



Mountains. 



QUALITY OF SECOND-GROWTH BARK. 



Tanners estimate that second-growth bark will average only 10 per 

 cent tannin, and when it was first put upon the market they objected 

 to it; but, mixed with virgin bark, it is now used to a considerable 

 extent. It is distinguishable from virgin bark by its peculiar smooth- 

 ness both on the outside and the inside; by its brittleness, due to lack 

 of fiber, especially toward the inside, where virgin bark is so fibrous; 

 and by its sappiness and light color. 



Table 9 shows the characteristics of samples taken from near the 

 bases of trees. The thinner bark higher Up would, of course, lower 

 the average. 



It is possible to produce a good quality of leather by tlie use of 

 second-growth bark alone, but a large quantity is required to offset 

 its low tannin content. The item of labor is also greater, since it costs 

 more to handle the extra bark. 



TABLE 9. Analyses showing tannin content of tan-oak bark taken from thr& 'Second- 

 growth trees. 



