UTILIZATION OF BLACK WALNUT. 33 
the saw. The older method was that of piling the lumber in a pit 
made of boards, at the bottom of which was the open end of the 
exhaust-steam pipe from the engine. The lumber was then covered 
over with sawdust and kept in the wet steam for several days. (PL 
IV, fig. 1.) The common method now is to build one or usually 
several large, fairly tight compartments with large doors and, after 
the lumber is piled in these compartments, to close them as tight as 
possible and turn in the steam. This method has the double effect 
of giving the wood, including the sapwood, a uniformly brown color, 
and of expediting the process of seasoning. There is usually not 
sufficient exhaust steam for this purpose, and live steam also must 
be used. Operators ordinarily steam their stock from four to five 
days at a temperature of 140° to 160°. If live steam is used it is 
difficult to regulate the temperature with the usual equipment; for 
when little exhaust steam is available more live steam must be used, 
and a higher temperature results. To regulate the moisture and tem- 
perature of the steam there is an equipment used in which the live 
steam is run over tanks of water ; as moisture is taken up, the tem- 
perature is reduced. 
Forest Service tests on walnut steamed for 10 days at a tempera- 
ture of 190° and at atmospheric pressure have shown a decided 
loss in shock-resisting ability, or " toughness," for the steamed mate- 
rial. It is likely, however, that no appreciable loss in strength prop- 
erties results from steaming at the usual lower temperatures. Cab- 
inetmakers report that they find little or no difference between the 
properties of steamed and unsteamed walnut as it is now placed on 
the market. 
Steaming gives a more or less uniform color to both heartwood 
and sapwood and makes the sapwood as valuable on the market as 
heartwood; for, according to the grading rules, any amount of sap- 
wood is admitted in steamed walnut. Steaming also shortens the 
seasoning period. Manufacturers claim that steamed walnut, prop- 
erly piled and air-seasoned, in 30 days will be as dry as unsteamed 
green walnut that has been in the pile for 90 days. Steamed walnut 
lumber 1 inch thick is considered to be " shipping dry " after being 
air-dried 30 days; and l|-inch steamed walnut is so regarded after 
being air-dried 45 days, or one week for each quarter inch in thick- 
ness. This procedure effects a great saving in the time required for 
seasoning. It is also claimed that the steamed lumber is not so sub- 
ject to fungus attack and discoloration when it is piled for air-drying. 
The amounts of different grades of lumber produced from walnut 
logs are very difficult to determine, because no two manufacturers 
use the same general class of logs for lumber, nor do they manufac- 
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