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?
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.
Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?
Have you reviewed the related Knowledge Base areas below?
KnowledgeBase: Primary Processing
KnowledgeBase: Primary Processing: Air Drying Lumber
KnowledgeBase: Primary Processing: Kiln Operation
KnowledgeBase: Wood Engineering: Wood Properties
KnowledgeBase: Knowledge Base
All rights reserved. No part of this publication may be reproduced in
any manner without permission of the Editor.
Review WOODWEB's Copyright Policy.
The editors, writers, and staff at WOODWEB try to promote safe practices.
What is safe for one woodworker under certain conditions may not be safe
for others in different circumstances. Readers should undertake the use
of materials and methods discussed at WOODWEB after considerate evaluation,
and at their own risk.
335 Bedell Road
Montrose, PA 18801
Copyright © 1996-2013 - WOODWEB ® Inc.