I have begun to not only appreciate wood but the art of working with it. Because of that I find myself very attracted to the intricacies of it. It’s no longer a piece of wood to me…each piece of wood has become an art piece that is delicately given to us on a daily basis. I’d like to begin a series of this interest and would love feedback and discussions surrounding it!
You love wood enough to make a hobby of it…right? Fabulous! However, it is important to learn some simple wood moisture content (MC) concepts so that you can safely build to your heart’s content.
As you work with wood, you measure its length, width, and thickness. You plane it to the required dimensional thickness. You make your joints between separate pieces. You fasten it all together with screws, nails and glues. However, not managing the MC of your wood can change all those measurements and possibly cause moisture related problems such as warping, glue line failures, splitting, or chipped grain problems, because moisture is an organic part of wood. In order to preserve the strength and durability that you expect from your wood project, you need to measure the MC of your wood material.
Wood and Water
MC is the amount of moisture inside wood. Every wood cell holds moisture in its nucleus (center) and in its walls. All trees naturally circulate moisture and nutrients from their roots to the tips of the highest branches, so moisture is a beautiful, natural wood characteristic.
However, MC varies widely based on the wood species. It is important to know the wood species used in your wood project so that you can determine the MC of the wood accurately. Hobbyists and professionals alike use a wood moisture meter to measure the MC so that inappropriate levels do not cause moisture related problems to the end product during service.
Wood, Water and Air
Trees have a higher MC in their original state (called “green”) than when they leave a lumber mill. “Green” wood is too wet usually for most wood product applications. Lumber producers invest millions in very complex forms of wood moisture measurement equipment to dry the MC of the wood from the green state to the appropriate MC level so hobbyists, builders and consumers can use the wood for their own end product applications.
When trees are cut, they no longer need to feed themselves with moisture and nutrients. However, keen hobbyists, like you, rely on strong, stable wood materials to use on wood projects. When a MC of a wood is balanced with the relative humidity (RH) and temperature of its surrounding air, wood has reached its prime state: its equilibrium moisture content (EMC).
However, even after wood has reached its EMC, changes in the RH in the surrounding air can influence the MC. When the surrounding RH rises, wood absorbs moisture from the air; when the RH falls, wood releases moisture into the air. Even seasonal weather changes may cause wood to shrink and swell as it interacts within the RH of its environment.
Where it becomes crucial for woodworkers is when this natural moisture migration process causes moisture problems: splitting, warping, or even dimensional changes in the wood.
The Tools for the Job
A wood moisture meter is a great tool for monitoring the natural give-and-take between wood and the RH and temperature of its surrounding atmosphere. Hobbyists and wood professionals both use a wood moisture meter to measure and monitor changes in the MC of the wood. Ideally, users should check the MC prior to project construction to ensure the quality of the purchased kiln dried wood and repeatedly as the project continues.
Wood moisture meters come with a variety of features, depending on the level of accuracy and information you require. Basic meters, like the pin-style Extech MO100, give air temperature and wood relative MC readings in a small inexpensive MC tool. More sophisticated wood moisture meters, like the pinless Wagner Meters MMC220 “Extended Range” meter, provide non-damaging wood MC readings programmable for domestic and exotic wood species. The MMC220 has a hold MC display feature and more advanced electromagnetic wave technology for greater accuracy of measurement.
A wood moisture meter is the best tool available for measuring and monitoring the MC of wood and for ensuring the success of each and every woodworking and wood flooring project.