FOREST PRODUCTS 181 



chipper or hack. This chipping is generally done once a week during 

 the warm season from March to October. Many studies have been 

 made to improve the method of chipping and collecting the resin. 

 Turpentining is generally conducted in units known as crops which 

 consist of a turpentine orchard of 10,500 faces. There may be 

 one, two, or three faces on each tree, depending upon its surface. 

 No tree smaller than 9" d.b.h. should be tapped for turpen- 

 tine. 



7. Cooperage. Cooperage is made from wood in three forms, 

 namely: staves, heading, and hoops. Tight cooperage refers to bar- 

 rels and kegs which contain liquid materials. Slack cooperage is used 

 for shipment of flour, sugar, lard, paint, meat, fish, vegetables, fruit, 

 hardware, crockery, and rosin. Since the repeal of the prohibition 

 amendment, the demand for tight cooperage stock has advanced very 

 materially. White oak is the principal wood used for tight cooperage. 

 For slack cooperage a great variety of inexpensive woods are used, 

 chiefly red gum, beech, birch, maple, tupelo, and southern pines. 

 Southern pine and white pine are preferred for heading. Elm is the 

 principal wood used for hoops. 



8. Tanning Materials and Dyewoods. These are compounds found 

 in various woody plants. Tannins are found chiefly in the bark and 

 leaves of some species, the chief sources being hemlock and oak bark, 

 chestnut wood, and sumac leaves and twigs. Imported sources of 

 tannins are quebracho from South America, wattlewood from Aus- 

 tralia, myrobalan nuts from India, and mangrove bark from the East 

 India tropics. Tannin possesses the property of precipitating gelatine 

 soluble proteins and alkaloids from solutions which, combined with the 

 skinned protein of animals, forms a durable, flexible, impervious prod- 

 uct known as leather. Formerly, natural vegetable dyestuffs formed 

 the principal sources of dye materials. Synthetic or coal-tar dyes 

 now dominate the market. The more important natural dyestuffs are 

 logwood from Central America, brazil woods imported from the West 

 Indies, brazil of the Bahamas, which yields hypernic and braziline, 

 fustic from the West Indies and Tropical America for yellow dyes, and 

 osage orange from the Southwest used in dyeing cotton, leathers, wood, 

 and paper. 



9. Wood Distillation. By the process of destructive distillation, 

 wood yields three primary products, namely non-condensible gas, 

 pyroligneous acid, and charcoal. In distilling the wood of southern 

 yellow pine, turpentine, rosin, and pine oils are obtained. Pyrolig- 

 neous acid is distilled to produce wood alcohol or methanol as well 

 as acetone, acetic acid, and wood tar together with other, less im- 



