64 BULLETIN 1136, U. S. DEPARTMENT OF AGRICULTURE 
ceptions in both directions. Quarter-sawed stock usually may take 
a more severe schedule than plain sawed, a fact which makes up for 
some of its natural slowness in drying. 
FINAL MOISTURE CONTENT 
The moisture content of lumber at the time the lumber is remanu- 
factured or is put into use largely determines the serviceability of the 
finished product and the satisfaction derived from its quality. A 
costly table made with some parts having 5 per cent moisture con- 
tent and others 15 or 20 per cent is almost certain to suffer severe 
damage from swelling of the dry pieces and shrinking of the wet 
ones during the process of moisture adjustment that must take place 
after assembly. Similar and equally unnecessary irregularities in 
house lumber often are the cause of cracked plaster and of immove- 
able or rattling windows and doors; these irregularities, however, 
are usually much greater in such lumber than in furniture stock. 
The degree of uniformity of final moisture content in the rough 
material determines the value of the finished product fully as much 
as the workmanship or as the species of wood; it is a part of the 
quality of that material. Since a faulty moisture condition of the 
rough lumber can ruin the finest product of the best plant and of 
the most skilled workmen, all phases of the matter are well worth the 
closest study. 
FACTORS INFLUENCING FINAL MOISTURE CONTENT 
In considering the final moisture content of a given lot of material, 
it is necessary to think of (1) the average moisture content of the en- 
tire lot, (2) the moisture gradient in each piece, and (3) the range in 
average moisture content of the individual pieces. Variations (@) in 
the initial moisture content of these pieces, (6) in theirdrying char- 
acteristics, and (c) in the uniformity of the temperature and the 
humidity throughout the kiln, all tend to prevent a uniform final mois- 
ture content. Hence the type of drying schedule and the manner of 
its application may have an important bearing upon the uniformity 
of dryness in the product. 
SOFTWOODS 
With softwoods, a very large percentage of the lumber is kiln dried 
at the mill. Sometimes the stock is machined immediately after it has 
been taken from the kiln, but common practice is to bulk pile the 
rough-dry stock in unheated sheds before machining it. Low grades 
of rough kiln-dried softwoods are sometimes bulk piled in the open. 
Extensive tests recently made in all of the principal softwood pro- 
ducing regions show that the moisture content of kiln-dried softwood 
lumber as shipped from the mill has a wide range and that, with the 
exception of one or two individual mills, there is not much difference 
in this respect among the various regions. 
Excepting common grades, only a small number of the boards of 
an average shipment, usually less than one-tenth of the total, have a 
moisture content above 15 per cent. The moisture content of the great 
bulk of such a shipment is between 5 and 15 per cent, with that of a 
