Effects of humidity swing

How does a swing in humidity affect drying time and MC gradient? February 28, 2001

What would be the effects of a "humidity swing" (raising the RH appreciably for a while and then returning to the original RH) on the drying time and the MC-gradient?

Forum Responses
It does very little for drying time (at atmospheric pressure), extending it only slightly. However, for some species, like oak, the rapid swelling of the surface with moisture gain will pull the interior and if there are small checks, they will grow deeper. Steaming before drying is an old technique that does have some benefit at times, but this is done before the wood dries.

Gene Wengert, forum technical advisor

Put a piece of hard maple someplace where the RH is above 60%. Move the same piece someplace where the RH is 30%. This will have the same effect as raising the pressure in a vac chamber and then pulling it back down.