Wood is simply that mass of tiny or thick long tubes of cell cavities, that runs the entire length of a tree. In these cell cavities, moisture exists as both “free water” and molecular water, which is tightly locked inside the cell walls. The moment a tree is cut or felled, the slow and gradual process of drying commences. All freshly cut (green) wood retains a lot of water, however, the moisture must be greatly removed before you can make maximum use of your wood. Whether you’re a woodworker that makes furniture, or a wood flooring professional that installs wooden floors, the moisture content (MC) of the wood should always be on your mind.
Because of their hygroscopic nature, wood easily gains or loses moisture as the relative humidity of the surrounding changes. As the humidity increases, the wood gains water, increasing the MC and causing the wood to expand. On the other hand, when the surrounding humidity decreases, the wood loses moisture, which causes it to shrink. When the wood reaches a state where it neither gains nor loses moisture, then it is assumed that the wood has reached its equilibrium moisture content (EMC).
How dry should wood be for woodworking?
The ideal moisture content for wood depends greatly on what the wood is used for, as well as the average relative humidity of the location where the wood would be used. For woodworkers, the ideal moisture levels for wood is between 6% and 8%, depending on the usage. For the construction of fine furniture, musical instruments, and other delicate wood products an even lower moisture content of 5% can be needed.
Freshly cut (green) wood can have a moisture content of between 40% to about 200%, depending on the type of wood. Any wood with this moisture content is considered unfit for both woodwork and firewood. Hence, before using the wood, it must first be dried to lower the moisture content. The ideal moisture content for wood depends greatly on what the wood is used for, as well as the average relative humidity of the location where the wood would be used. It is very important to dry down the wood you’re working with, to moisture content within a 2-percentage point of the equilibrium moisture content of that location. Do you want to know how dry your wood should be for woodworking? Then you’re in the right place. This article will guide you through everything you need to know about the moisture contents of wood and how dry it should be for woodworking.
Contents
The Right Moisture Content of Wood for a Woodworker
Two major factors determine the acceptable moisture content of wood. They include; the final use of the wood and the average relative humidity of the location where the wood will be used. These two factors makes the optimal moisture level different in different locations.
Generally, wood shrinks and warp as they dry; this is why woodworkers need it to be completely dried before they use it. If the wood dries and shrinks after they use it, it will damage their work and cause permanent problems. To minimize the shrinkage of wood after use, you must first dry it to a moisture content of around 8 percent as a woodworker.
Freshly cut or green wood can attain a moisture content level of 40 to 200 percent, and the acceptable or normal moisture content for woodworkers varies from 7% to 19%, depending on the relative humidity of the surrounding air. Specifically, woodworkers who major in the construction of fine furniture, dishes, musical instruments, decorative pieces, toys, and other wood products, can only work with wood ranging from a moisture content of 5% to 9%. However, this range can vary depending on the relative humidity levels of the geographic location.
How to Measure Moisture Level in Wood
There are two different ways to measure the moisture level in wood: you can use a moisture meter or an oven-dry testing method. Moisture meter testing is undoubtedly the easiest method, which is why we have explained it below:
● Moisture Meter
This is the easiest and most efficient way to test for the moisture content of the wood. However, there are two types of moisture meters that you can use. The pin-type moisture meter makes use of penetrating metal probes that measures the wood’s moisture level via resistance. Since water conducts electricity and wood cannot, dry wood will produce more resistance than wet wood. To achieve better results, you’ll have to insert the pins of the moisture meter (with little pressure) into the surface of the wood that you want to test. Make sure that the pins align with the grain, then turn the meter on and measure the moisture content.
Pin-less moisture meters do not penetrate the wood, instead, they scan the wood using an electromagnetic sensor and measure the moisture content. Because these moisture meters usually cover more surface than their pin-type alternatives, they often provide a better idea of the moisture present in the wood. Another advantage of this pin-less meters is that they don’t leave any pinhole damages on the surface of your wood. This is why they are the more preferred option by those that deal with expensive wood materials. Pin-less meters are also quite easy to use. Simply place the scanning plate against the surface of the wood and turn on the meter to measure the moisture content.
How to Air-Dry Wood
● Stack Your Split Wood with Spacers
Pick an ideal area ideal for stacking, that is, an outdoor area with little or no shade for maximum solar drying. To properly utilize the air, choose an area that is very open to prevailing winds. Try and avoid areas that are prone to flooding or standing water as these will reduce the drying time. To determine the direction of the prevailing wind, you can hold a light material in the air; whatever direction it flows to is most likely the direction of the prevailing wind.
● Create a Raised Bed
Make sure your firewood is not in contact with the ground as moisture may collect below, causing it to rot. You can use any material that won’t absorb water, such as a grid made of horizontally-placed poles. You can also use wooden materials like lumber or pellets that you longer have a use for. If you’re using a wooden bed, line the top of the bed with tarps, plastic sheeting, or any material that can block the transfer of moisture from the wood underneath to the wood on top. Also, make drainage holes in the materials to avoid water pooling on top, making the wood drying faster.
How to Tell If Wood Is Dry
● Color:
While color varies from species to species, your wood should grow darker as it dries. Seasoned wood tends to be less vibrant than greenwood.
● Size:
Splitting up your wood ultimately reduces the drying time. If you need your wood shortly, it is best to purchase the ones that have already been split. Split wood will dry out faster than stacked-up whole logs.
● Weight:
As wood dries, it loses its moisture weight and becomes lighter. The difference in weight is an indication that the wood is dry. When you first split the wood, take note of how heavy each piece feels. The same piece should weigh less once it loses moisture weight.
● Bark:
To know if your wood is dry, most or all of the bark should have fallen off on its own. Any existing bark can be removed easily. You can slice the bark off using a knife and inspect the wood underneath. If any pieces appear greenish, then it needs further drying.
● Split test:
Dry woods are usually quite hard to split when compared to the greenwood. Dry woods are also usually dry on the inside. To check for the moisture level of a piece of wood, you can split it open to know if it feels dry to the touch.
● Sound:
To know if the wood is dried, strike two pieces against themselves. If they produce a hollow sound instead of a dull one, then you’re good to go.
● Smell:
Greenwood has a sappy aroma, which often depends on the type of tree. As the wood dries, the sappy scent will gradually fade into a light woody smell.
● Flammability test:
You can test the moisture level of wood by test-burning a few pieces outside. Greenwood will be difficult to light and will smolder, creating a lot of smoke instead.
● Moisture meter:
This is the most accurate way to test for the moisture content of your wood. When you insert the meter into dry wood, the reading should be below 8% for woodwork and below 20% for firewood. You can get a simple moisture meter at any hardware store.
Final remarks
For woodworkers, the ideal moisture levels for wood is between 6% and 8%. Before you use wood for any project, ensure that the moisture content is at the acceptable level. If you ignore this, the wood might end up shrinking, cracking, expanding, or warping, and this may cause major problems in your project. Once you have dried your wood, use a moisture meter to measure the wood’s moisture content. If it is higher than the ideal level, dry the wood further before using it for your project.