164 



TANNING MATERIALS AND TANNERIES 



II. The bark or else the wood is shredded in a chipper and the 

 tannin extracted (not entirely) by steam or hot water. The liquid obtained 

 is condensed in the vacuum. 



Cold Water ^ 



Injection Q L 





Condensei 



mi-^^^? 



ayc»gi>j!^-g-B?ag.4^a''-'a-?'e?^.-i'',- « j^ -- = j^b,? „ '^s".^^,?A,^rg'^ ^^ ; 



Liquor Feed 

 Line 



Return to 

 Boiler 



Cotidetisadon 

 Drain 



Condensation 

 Drain 



Condenser 

 LegPioe 



Triple effect Zaremba evaporator for condensation of tannic acid. Zaremba Co., Buffalo, N. Y. 



ill. While in France the sappy branches and young shoots of chestnut are preferred, in America the 



heart wood and especially the butt is considered best. 



IV. The wood is cut 4 feet to 5 feet long. The South uses a cord of 160 cubic feet = 1' 4 cords of 



128 cubic feet in the chestnut wood business. 



V. Clear water, cheap transportation, and cheap fuel are required for successful manufacture. Only 

 sound wood is used. Worm holes in chestnut, however, do not interfere with its tannic value. 



VI. Liquid extracts exposed to air or exposed to heat spoil rapidly. 



VII. Chestnut extract is shipped in barrels of 56 gallons capacity or in tank cars. .Wore rarely, it is 

 condensed to a solid form and shipped in sacks. 



VIII. The price of chestnut extracts is 1' ,c to 1' oC per pound. 



IX. Rarely in the United States, but usually in France, chestnut extract is bleached so as to prevent 

 it from imparting a dark color to the leather. 



X. One cord (160 cubic feet) of chestnut wood yields one barrel or 500 pounds of extract containing 

 about 25 per cent tannin, and worth •v6"50 to ^'SOO. 



(F) CRITERIA OF A GOOD METHOD OF LEATHER MANUFACTURE are:- 



I. The weight of the leather produced. Since leather is sold by the pound (excepting army orders), 

 the tanner tries to press into the hide the maximum amount of tannin, tannin being cheaper than hides. 



Beyond a certain point, this extravagance of impregnation fails to increase the wearing qualities of 

 leather and is therefore useless to the buyer. 



II. The color of the leather produced and the adaptability of the leather to coloring. 



III. The possibility of ths tannin being washed out through wear and tear. 



