TANNING MATERIALS 



73 



AVERAGE YIELD OF CHESTNUT OAK BARK IN CORDS FOR TREES 

 OF DIFFERENT DIAMETERS 



CHESTNUT EXTRACT 



The discovery of a method whereby the tannin content of chestnut 

 wood could be extracted and placed on the market to compete suc- 

 cessfully with other tanning materials, has brought about many changes 

 in the tanning industry, particularly within the past fifteen or twenty 

 years. More than two-thirds of all the tannic acid products made in 

 the United States is now derived from chestnut wood. 



The extract of tannin from chestnut wood is largely confined to the 

 southern states, particularly in Virginia and North Carolina. The wood 

 in those locahties contains from 6 to 11 per cent of tannin, whereas, 

 although the chestnut tree is commonly found in the northern states as 

 well, it does not contain a sufficiently high percentage of tannin to make 

 its extraction as profitable as that in the South. Chestnut extract is 

 commonly used in mixture with other tannins. 



The growth of the chestnut wood extract business has been very 

 rapid. In 1900 only 64,043 bbl. were used, whereas by 1906 the total 

 value of this extract was over two-thirds of the value of all extracts used 

 in the United States. 



The process of manufacturing chestnut extract consists of chipping 

 the wood in a " hog." These machines will grind around 5 cords per hour. 

 Some plants use disk chippers similar to those used in a wood pulp 

 reduction plant. There are several separate processes used in the 

 extraction of tannin from the chestnut wood, but the following is probably 

 the most common one employed. The finely ground chips are placed in 

 large cylindrical wooden tanks. The tank is flooded then with weak 

 liquor heated to a high temperature. The liquor is continually passed 

 from extractor to extractor and the process continues froin two to four 

 days. The process is usually carried on in batteries of 10 extractors. 



