Drying Rates of Different Wood Varieties

Drying rates are complicated because they depend on wood density as well as other factors. October 19, 2013

To what extent is the drying rate in a solar kiln dependent on the species?

Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
The kiln I designed (VA Tech kiln and other similar names) is designed to dry oak (when the kiln is full) safely. Species that can dry faster will be ok or may dry too slowly and not be as white as possible (unless the kiln is not loaded to capacity). Drying rates are given in Drying Hardwood Lumber, page 99.

From the original questioner:
I did find the maximum safe drying rates but I was looking for something along the lines of comparative drying rates. That is, under the same conditions species X dries two times faster that species Y. Is there any information along those lines?

From Gene Wengert, forum technical advisor:
Assume you have a piece of basswood and the same size piece of oak. They are both at 70% MC. Now they dry to 68% MC. For the basswood, this is a loss of 2% MC or about 1/2 pound of water. For the oak, a 2% MC loss will be close to 1 pound of water. So, if they both lose 2% MC, the oak is actually drying nearly twice as fast in terms of the amount of water lost.

When freshly sawn, all wood will lose about the same pounds of water, as the process is controlled by the evaporation at the wood's surface. As drying proceeds, the wood itself begins to control the process with denser woods losing less pounds of water. Of course, in a kiln we control the rate of loss mainly by controlling the humidity so we will see different rates for different species. So in answer to your question there is no simple answer or set of numbers.

From the original questioner:
I have just finished and loaded my kiln with a mixture of oaks (white and red) and yellow poplar. So if I understand correctly, when the oaks are where I want them the Y-P will be wherever it is.