Ratios: Relative humidity to moisture content
Common conversions and instruments used in measuring wood moisture content. October 31, 2000
What is the conversion scale between RH and MC? For example: 75% RH = what amount of MC? Also what do you call the gauge used to measure these? I am trying to control the moisture in a room, and I would like to see which of my methods works the best.
A hygrometer measures humidity. A thermo-hygrometer measures humidity and temperature. A psychrometer has two thermometers (one wet and the other dry) that measures temperatures and can be used to calculate humidity.
The property of the air is called the equilibrium moisture content (EMC) and it is numerically equal to the MC that wood will achieve during drying if you wait long enough and if the conditions do not change. (Example: At 30% RH, wood will achieve 6% MC. So the air has an EMC of 6%.)
0% RH = 0% MC = 0% EMC
30% = 6%
50% = 9%
65% = 12%
80% = 16%
99% = 28%
Look in the archives for more discussion.
Gene Wengert, forum technical advisor
For a great table on the relationship between relative humiduty, room temperature, and equillibrium moisture content visit www.furniturecarver.com/emc.html.
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: Woodworking Miscellaneous: Accessories
KnowledgeBase: Lumber & Plywood: Storage
KnowledgeBase: Primary Processing: Air Drying Lumber
KnowledgeBase: Primary Processing: Kiln Operation
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.