Last Updated on February 16, 2022 by Barry Gray
To work with wood and achieve the most precise cuts and best finishes, you need to understand the part moisture in the surrounding air affects it. Whether you are constructing furniture, installing wooden floors, undertaking any wood carving, or practicing carpentry, the moisture content of wood should always be factored in.
Wood should be dried to within 2% of the humidity where the wood piece will be installed. In practical terms, let’s assume the humidity range is 18 – 26%. The equilibrium moisture content would be 8% (26-18%), and the wood moisture content needs to be 8%.
Equilibrium moisture content is the moisture level at which the wood neither gains nor loses moisture; this measurement is used to assess the wood’s readiness to be worked. Wood with incorrect moisture content will warp, and the joints will crack, making them unsightly.
Wood Moisture Must Be 2% of The Equilibrium Moisture Content.
Equilibrium moisture content is when wood stops absorbing moisture from the atmosphere or releasing moisture into the surrounding air; this is when the wood reaches equilibrium with the surrounding air.
Different locations have varying levels of humidity. When calculating the Equilibrium Moisture Content, we use the range average minimum and maximum humidity levels in that area.
If the humidity ranges from 19% to 26%, the Equilibrium Moisture Content would be 7%.
The wood’s moisture content must fall within 2% of this figure (5% – 9%).
How To Ensure Wood Has The Right Moisture Content
The easiest way to match the wood’s moisture content with the Equilibrium Moisture Content is to source wood from the same area where it will ultimately be used.
If this is not possible, you can use two primary methods.
First, measure the moisture content of the wood you propose to use. To do this, you will need a wood moisture meter.
As the name implies, a wood moisture meter is a device that measures the moisture content of the wood. The meter has two probes that you touch against the wood. The meter measures the resistance of the current between the probes. The lower the resistance, the higher the moisture content and visa-versa.
The Traditional Method Of Drying Wood
This method works well and will reduce the moisture content of the wood over a reasonable timeframe.
- Evenly lay out a series of already dried logs or planks about 16 inches apart. These are called stickers.
- Lay the wood you want to dry on top of the stickers
- The wood should be placed perpendicularly on the stickers
- If you’re going to dry more than one layer of wood, you should alternate the layers of moist wood with layers of dry lumber; this will result in a layer of stickers, moist wood, more stickers, moist wood, etc.
- Finally, place a piece of plywood on top of the pile.
- Weight the plywood down with something heavy, e.g., bricks, cinderblocks
- The objects that weigh the pile down must be weighty and evenly spaced on top.
- As the wood dries, it warps. The weight on top of the pile must be sufficient to stop the warping.
The warmer and dryer the climate, the faster the wood will dry.
Alternative Methods Of Drying Wood
If you work in an area with a high moisture content or want to speed up the process, there are several methods you can choose.
Kilns Are Very Effective In Dry Wood.
If you have access to a suitable wood kiln, this is the most efficient and effective way to dry wood.
- Wood kilns will dry wood to a controlled moisture level within a few hours.
- It’s important to remember that we are aiming to dry wood to the same moisture content as the Equilibrium Moisture Content of the area. Even wood dried in a kiln will have varying moisture contents depending on the kiln.
- Drying wood in a kiln is the least likely to warp or crack.
- Kilns have limitations on the size of the wood piece to be dried. The wood must be able to fit inside!
Humidifier With Fans Are An Effective Way To Dry Wood
Humidifiers are a fast and low-cost way to dry wood. They work by reducing the moisture content of the whole area in which they work.
Wood is a hygroscopic material. This means that it absorbs moisture from or releases moisture into the atmosphere until it achieves a balance with its surroundings. As the humidifier reduces the moisture content of the surrounding air, the wood releases moisture and starts to dry.
You need to keep in mind specific considerations when using a humidifier.
- Drying wood with a humidifier only works if you are drying your wood indoors.
- Advocates of humidifiers say that because humidifiers dry wood slower than kilns, the final product has a higher quality than kiln-dried wood.
- Humidifiers increase the heat of the space in which they work. If the humidifier is in your work area, the heat will increase, and you may need to install a cooling device.
- As with the traditional method discussed previously, it is beneficial to lay the wood out in the same manner: a layer of stickers, moist wood, more stickers, and moist wood.
- Wood being dried by a humidifier should be clamped together to stop warping or cupping by the process.
Humidifiers dry wood, but they also help protect your tools from condensation moisture and rust if it is running in your workshop.
Utilizing both a dehumidifier and a high-volume fan for air-drying your wood is something to think about as it speeds up the drying time of the pure humidified process.
Some More Thoughts On Drying Wood
Many homes have an HVAC-controlled environment. If you kept your woodshop at those levels, the kiln-dried lumber in your shop would be well matched to standard humidity levels of the home, with climate control in which it is installed. Your project would experience the least amount of wood movement as a result.
High-quality furniture that lasts for generations is built with joinery techniques that allow minor seasonal movement. Building in a little “give” to move slightly with varying humidity instead of fixing it rigidly in place is very important to not having joinery failures later.
It is a great idea to have a humidity sensor in your workshop; this means you only need to run the humidifier when required and lower your electricity costs.
It is essential to ensure that the moisture content of the wood falls within 2% of the Equilibrium Moisture Content of the final resting place of your project.
If you don’t, the wood may warp, and unsightly cracks may develop in the joints.
Each of the available methods to achieve this will depend on your situation and the facilities you have available.