of the given space; the less the relative saturation the
lower the dew-point.

Careful piling of the material to be dried, both in the yard and dry
kiln, is essential to good results in drying.

Air-dried material is not dry, and its moisture is too unevenly
distributed to insure good behavior after manufacture.

It is quite a difficult matter to give specific or absolute correct
weights of any species of timber when thoroughly or properly dried, in
order that one may be guided in these kiln operations, as a great deal
depends upon the species of wood to be dried, its density, and upon
the thickness which it has been cut, and its condition when entering
the drying chamber.

Elm will naturally weigh less than beech, and where the wood is
close-grained or compact it will weigh more than coarse-grained wood
of the same species, and, therefore, no set rules can be laid down, as
good judgment only should be used, as the quality of the drying is not
purely one of time. Sometimes the comparatively slow process gives
excellent results, while to rush a lot of stock through the kiln may
be to turn it out so poorly seasoned that it will not give
satisfaction when worked into the finished product. The mistreatment
of the material in this respect results in numerous defects, chief
among which are warping and twisting, checking, case-hardening, and
honeycombing, or, as sometimes called, hollow-horning.

Since the proportion of sap and heartwood varies with size, age,
species, and individual trees, the following figures as regards weight
must be regarded as mere approximations:

POUNDS OF WATER LOST IN DRYING 100 POUNDS OF GREEN WOOD IN THE KILN

=========================================================================
|Sapwood or | Heartwood
|outer part | or interior
=========================================================================
| |
(1) Pine, cedar, spruce, and fir | 45-65 | 16-25
(2) Cypress, extremely variable | 50-65 | 18-60
(3) Poplar, cottonwood, and basswood | 60-65 | 40-60
(4) Oak, beech, ash, maple, birch, elm, hickory,| |
chestnut, walnut, and sycamore | 40-50 | 30-40
=========================================================================

The lighter kinds