Wood Drying Process Essentials for Woodworking Projects
Did you know that most of the wood that you’re buying, whether from a lumber yard or home improvement store, has probably been through some kind of drying process?
And knowing the type of wood drying process used can help empower you as a consumer by giving you the knowledge you need to make the right decision for your woodworking project. That’s why, on this page, we are going to give you essential information about different types of wood drying.
We’ll talk about:
- The different types of wood drying processes
- Why drying/dried wood is so important
Let’s start with the key question of this article: what are the different types of wood drying processes?
Different processes of wood drying
When it comes to drying processes, there are really two to choose from: air drying and kiln drying. While these processes ultimately have the same goal—to dry wood—the ways they get to that end result are very different, and the quality of the dried wood a given method produces can also vary.
We’ll talk about both of these processes and cover what they are and how they differ from each other.
Air drying lumber
Air-dried wood is exactly what it sounds like: wood that has been dried by the air. This happens naturally—usually in the open air—and over a long period of time.
And while it may sound simple (all you need is wood and air, right?), air drying wood is actually quite complicated.
Well, it comes down to a few components:
- Unstable drying environment
- Space limitations
These three components all connect to help us understand how air drying works and how tricky it can be.
Unstable drying environment
When you air dry wood, your progress is at the mercy of the elements, which makes the drying environment unstable and impossible to control. This, in turn, makes it difficult to know how long wood will take to dry.
If you are in a hot, dry climate (think, Arizona) your wood will certainly dry faster than if you are in a humid climate with frequent rain (think, Florida). In other words, different places have different equilibrium moisture contents (EMC).
The lack of a controlled drying environment means that wood drying will largely slow down during cold winters and speed up during the summer.
This speed may sound positive, but according to the Wood Handbook, “hot, dry winds may increase degrade and volume losses.” 1 This ultimately results in an increased possibility of surface checking, end splitting, and other drying defects.
If, on the other hand, you are in a more humid climate, the lack of air movement can result in the growth of fungus.
Even if the climate is somewhat favorable for air drying lumber, the process still consumes a lot of space.
This has to do with the way that wood must be stacked for optimum drying.
In order for wood to dry evenly, there needs to be a good amount of airflow on all sides of the planks. The solution, then, is to stack the wood on spacers, or “stickers.”
While this does help the wood dry, it also takes up a good amount of space, and unless you have a lot of extra space, air drying wood could be very difficult.
The cost of storing this much inventory for such a long period of time also complicates air drying.
Air drying, then, will ultimately increase the cost and timeline of your project. It requires much more space and foresight.
All this being said, air drying certainly isn’t an impossible practice, but these complicating factors are important to consider before making it your main drying method.
Kiln drying lumber
Kiln drying is a drying method where, rather than placing the wood outside to dry, the wood is placed on spacers inside a kiln. The kiln is almost like a large oven in that it uses high temperature and air circulation to speed up the drying time.
Kiln drying is nearly opposite to air drying in almost every single way. Where air drying is uncontrollable and slow, kiln drying is carefully controlled and much faster.
While this might sound simple, kiln drying is somewhat of an art. It requires that the individual(s) running these kilns pay close attention to how the wood is drying.
Is the wood drying too quickly? Has it overdried? Are the pieces of wood coming out warped or with end checks? Is there a proper amount of humidity released within the kiln to keep the wood from degrading?
All of these questions are essential for a commercial kiln drying operator to ask.
Kilns also run on kiln schedules.
These, according to the Wood Handbook, “control temperature and relative humidity in accordance with the moisture content and stress situation within the wood, thus minimizing shrinkage-caused defects.”2
Furthermore, different types of kilns may function differently, and different wood species will also dry differently. Drying lumber using a kiln truly is a nuanced process, no matter how controlled it is.
Despite the artistry it takes to properly dry wood with a kiln, kiln-dried wood is less expensive than air-dried wood, which means that it is a more time- and wallet-friendly option. This will help your project’s bottom line.
Now that you know some of the basic differences between air-dried and kiln-dried wood, let’s talk about why it’s important to use dried wood in your projects.
Why should you dry wood for your project?
Making sure that you have dried wood for your project is also making sure that your project will succeed.
Wood is a living material. It shifts and changes depending on the moisture and temperature around it. If there is little moisture in the air, the wood will release moisture and vice versa.
This means that if you use green lumber (wet wood) in a woodworking project, your project may suffer as the wood changes. It may develop warps and cracks, or it may shrink.
Not only is this disappointing because you put time and effort into a project, but it’s also harmful to your reputation and your bank account.
What if a client gets a project, and in a few weeks, it begins to warp and crack? At that point, your reputation has suffered, you’ve wasted time, and you need to remediate the situation, meaning your bottom line will suffer too.
Dried wood is a priority for any project. While you may think it a benefit to dry your own lumber, both air drying and kiln drying can be difficult for most woodworkers unless you either have surplus space or your own kiln.
This means that, for most, project success begins with purchasing dried wood, whether that is air-dried or kiln-dried.
But what is the best way to know if the wood you are purchasing is dry?
By using a wood moisture meter!
This will ensure that you are purchasing wood that is at the proper wood moisture content for your project and for your area.
A pinless moisture meter, like the DS500 from Bessemeter, can come with you to the lumber yard or construction store. You can scan the wood right then and there, and you can feel confident about your purchase.
If you are interested in making wise buying decisions and ensuring that your wood has been properly dried, consider adding a moisture meter to your toolbox.
- Wood Handbook, p. 13-6. (↑)
- https://www.fpl.fs.usda.gov/documnts/fplgtr/fplgtr282/fpl_gtr282.pdf, pp. 13-6. (↑)