322 PLANTS AND MAN 



greatly during recent years. It is lustrous, of a soft texture, and of 

 a constant color, and can be used to advantage in combination 

 with cotton, silk, satin, and wool. The manufacture of rayon is 

 intricate and complicated, there being four different processes 

 by which it is made. There are about twenty five factories in the 

 United States, which is the worlds principal producer and user of 

 rayon. Further discussion of this product, as well as the one fol- 

 lowing, are to be found in Chapter 23. 



Plastics. — The field of wood plastics is relatively new and 

 undeveloped among the forest industries. It consists of the mold- 

 ing of pulp or cellulose products under great pressure to yield a 

 hard substance which will not shrink or swell with moisture 

 changes. With the great volume of previously mentioned sawmill 

 and woods waste that is available at low cost for production of 

 plastic products, it is reasonable to believe that in the future this 

 industry will yield many products used in art, architecture, build- 

 ing construction, novelties, and other useful commodities. The 

 nature of the processes by which plastics are produced is further 

 elaborated in Chapter 23. 



Hardw^ood distillation products. — ^The process of con- 

 verting wood into charcoal has been carried on for as long as 

 there is recorded history. Of course, it is only in recent times that 

 the gases, which pass off from the carbonizing wood in the form 

 of dense, heavy, black smoke, have been of economic value. The 

 northern hardwoods, maple, beech, and birch, are the most 

 desirable, but oak and hickory are also very important, and as a 

 result the industry centers mainly in the Lake States, New York, 

 Pennsylvania and Tennessee. The annual consumption of wood 

 by the hardwood distillation industry is between one-half and 

 one million cords, or about six- tenths of one per cent of all timber 

 cut. In the process of manufacture, the wood is cut to fifty inch 

 lengths, loaded on small metal trucks, and run directly into large 

 iron ovens. The wood is heated, by fires built beneath the ovens, 

 for twenty two to twenty four hours, during which time all gases 

 are driven off and condensed into large tanks. After completion 

 of the heating process, the charcoal is moved into a set of cooling 

 ovens for twenty four hours, then into the open air to cool for 

 forty eight hours. Caution is necessary in cooling the charcoal 



