68 BULLETIN 1136, U. S. DEPARTMENT OF AGRICULTURE 
and “ air-dried,” or even “ thoroughly kiln-dried ” and “ thoroughly 
air-dried.” ‘These terms are so indefinite that they really are without 
significance. Unfortunately there are at present no universally ac- 
cepted standard moisture specifications, so that each purchaser must 
draw his own. The moisture clause in a seasoning specification is 
fully as important as a grade specification—sometimes much more 
important. For many reasons it is essential that the purchaser know 
certainly that he is getting stock dried to the degree proper for his 
needs. ‘The vendor also should know positively, and at the very be- 
ginning of the transaction, what the purchaser wants. Accurate 
specifications, expressed clearly and definitely, are of high value to 
all concerned. 
DRYING STRESSES 
Although specifying the amount of moisture that purchased stock 
should contain either at the time of shipment or on receipt is excel- 
lent in every way, it is not always sufficient, since the seasoning con- 
dition of two lots of similar material dried to the same average mois- 
ture content may be vastly different. A workable seasoning specifi- 
cation will contain a clause, based upon the use of stress sections, 
covering drying stresses in the rough stock. In explicit form such 
a clause, even if only reasonably complete and only commercially 
accurate, may be unduly long and cumbersome. A simple statement 
that the wood shall be free from injurious drying stresses, however, 
although very broad will still afford reasonable protection to both 
purchaser and vendor especially when inspection by means of stress 
sections is definitely permitted. In fairness to the vendor, informa- 
tion about the probable uses of the stock, expressed more or less 
briefly, should be included. 
STORAGE OF KILN-DRIED STOCK - 
Since all of the pieces in the kiln are not of the same moisture 
content at the end of the drying period, it is desirable that they 
be held in storage until both the dry and the less dry ones approach 
closely an identical moisture content. The time required for such 
storage varies with conditions. One week is considered long enough 
for furniture stock, and two weeks are specified for aircraft stock. 
Caretul conditioning in the kiln reduces the time desirable in storage. 
Dimension stock and finished wood products that have to be stored 
should be held in proper atmospheric conditions, for otherwise they 
will absorb or will lose too much moisture. Later, when the stock 
has been remanufactured and is in actual use, this gain or loss may 
damage its serviceability. 
When dry stock is bulk piled in a damp storeroom, the exposed 
ends of the boards pick up moisture rapidly, the exposed edges and 
sides do so more slowly, and absorption in the interior of the pile is 
quite slow. Asa result of this situation the moisture content of the 
entire pile will gradually become too high and, further, the moisture 
distribution in individual pieces and the moisture range among differ- 
ent ones will be unsatisfactory. Short stock, with exposed end 
surfaces, is very liable to trouble resulting from storage in damp or 
unheated storerooms. 
