Wood can be a tricky construct to work with. Trees need water to survive, because of this wood is deliberately created to hold moisture. Even when separated from the entirety of the tree, and turned into lumber, wood’s sponge-like properties do not go away. Because of this, it is imperative that we always check our wood’s moisture content to evaluate if a project is dry enough. Wood that carries too much moisture, has more opportunity for shifting, shrinking, warping, cracking, and splitting.
An easy, quick way to find out moisture content is to get yourself a moisture meter. This product can be found, in different varieties, at your local hardware store or Home Depot.
There’s two specific types of moisture meters, pin-type and pinless.
Pin-type meters use electrodes to determine the wood’s moisture content by sticking the pins, of the reader, into the wood. The machine determines how much resistance is being given from the wood to the meter’s electric current. Because water conducts electricity and wood does not, the more moisture in the wood, the less resistance to the current. Therefore, the dryer the wood, the more resistance it will carry.
Tip: Test multiple spots with the moisture meter. Wood does not dry equally and this will aid in assuring you get a true, accurate reading. An optimal level of moisture is around 6% to 8%. While working on something a bit higher is acceptable (up to 14%), try your best to get that wood to be as dry as possible.
The other type of moisture meter is a pinless one. The pinless meters read moisture content without penetration to the wood by scanning the wood’s surface. However, because pinless meters can only scan to a certain depth the accuracy of the reading would also be determined by the thickness of the cut of wood. Regardless of which meter you use — pin-type or pinless — both will need multiple readings. Keep this in mind when purchasing a moisture meter, especially because a pin-type will leave holes and blemishes behind.
Kiln/Oven Dry & Ouside/Inside Drying
If you’ve purchased wood from a millwork, before, you’re probably familiar with the oven drying method. This particular method, while time consuming, can be wonderfully accurate when done properly. A piece of wood is placed within a kiln or wood oven and its initial weight is recorded. The piece of wood is then left in the oven to dry, at a consistent temperature, until the wood’s mass no longer varies; this stop in fluctuation provides evidence that the wood has reached an optimal level of moisture and is ready to be used.
This method of drying is not only great for ensuring workable wood, but also for eliminating mold and pest infestation the wood maybe carrying.
Unfortunately, these systems are expensive and need a bit of room to house, which is why many stick to owning a moisture meter and rely on buying kiln wood in times that are specifically necessary.
If you do happen to find yourself in a situation where you need to store wood for drying, the best way is to leave it outside — stacked with spacers between each slab and covered — until the wood reaches a moisture of about 15% to 20%. After, to further reduce the moisture content, bring the boards inside for a period of time to dry. In time, they’ll eventually reach an appropriate moisture content.
No matter what method is comfortable for you, understanding moisture content, and knowing how to find it, will aid in reassuring those beautiful wood pieces are always project ready!