"Mike Marlow" wrote in message
...
You are incorrect. The fibers will expand and contract when the
moisture
gets to them, and at the same rate, less compression set. You may slow
the
arrival with occlusive finishes, but wood loves water and will find a
way.

This does not make sense George.

It does to wood technologists. RH correlates directly to moisture content.


Wood fibers that are constrained can only
absorb water to the point that they equal the force placed on them by the
joint. At that point they effectively reach their saturation level. Wood
does not continue to obsorb moisture until it reaches the point that its
moisture content is equal to the surrounding air, it absorbs it to a
maximum
it can hold and that maximum is limited by the cell's ability to contain
that moisture. Constrain those cells and they are capable of holding less
moisture.

Incorrect again. The fibers adsorb moisture at the molecular level, binding
to the cellulose. There is a lot of air left inside any board, indeed,
inside the cells themselves, which spaces are shrunken by the inexorable
gathering of moisture, though they do compression set - they don't return to
full expansion - which condition exacerbates the one caused by shrinkage of
the fibers themselves once the wood begins to seek EMC with lower RH.

Wonderful, well-documented stuff here
http://www.fpl.fs.fed.us/documnts/fp.../fplgtr113.htm to read.
Start with chapters 2 and 3.