As a woodworker, this is a question you will encounter more that one time in your shop.
It’s an important question because it deals with the moisture content of the wood. The moisture content of wood has to do with the amount the wood will move, shrink or expand. To not understand wood movement can end in disastrous results. So to help answer the question lets get some basics of what’s happening and the pros and cons of each method.
Wood obviously is not a living thing as it was when it was a tree. But it will always be constantly moving as if it was alive. I like to think of wood like a sponge. A sponge when it is dry is small. But when it absorbs water it can expand greatly in size. Wood takes in the water from the humidity in the air. Different regions where we live can have different levels of moisture in the air. Living in northwest Ohio, wintertime the humidity gets very low. Low humidity means the moisture leaves the wood causing it to shrink in width. In the summertime, the humidity here can be 91% making the wood expand in size. Knowing the moisture content in the board you are working with is important. The wood needs to be able to move freely so it doesn’t cup, warp or worse, split and crack.
The ideal percentage of moisture in a board should be 5-9% and a moisture meter can be used to get a reading of the wood. But how does the board get to this ideal percentage? The answer is by either air-drying the wood or using a kiln.
Kiln Dried Wood
A kiln is like a furnace. The wood is placed inside at a temperature of around 170 degrees. This controlled environment of temperature and humidity speeds up the time to dry the wood by collapsing the cells in the wood. This is a fast way to bring the wood down to the “ideal” moisture content.
Kiln-dried wood changes the color of the wood making it lighter by as much as 20%.
It also makes the wood more brittle and is harder on tool edges such as saw blades and chisels.
Wood that is rushed too fast in a kiln can produce internal tension in the wood. Meaning, as the wood is cut it can bind and pinch together. It also can result in “shake”. Shake is a form of cracks that happens in wood that is dried too fast.
Kiln wood can cost more than air-dried wood because of the drying process.
Air Dried Wood
Air-dried wood is a much slower process. It needs one year of drying for every inch think. So if the board needs to be 2” thick, the wood has to sit for at least 2 years.
Waiting for the wood to dry means a lot of room has to be devoted to it just sitting there.
Air-dried wood is cheaper than kiln-dried.
It is softer than kiln dried and is easier on tool edges and it keeps all of its colors.
Air-dried wood will move more in seasonal changes than kiln-dried.
So at the end which is better? Well, that depends on the individual. If you are wanting to build something right away, spend the extra money and purchase kiln-dried wood.
If you are planning for future builds air dried is a good way to go and easier on the wallet.
Either way, it’s a good idea to ask when you buy lumber if it has been air-dried or kiln-dried.
I get almost all my lumber at Kencraft. It’s a family run business and I have been going there for at least 15 years. If you have any question they will be happy to help you.
Chad Stanton- Owner of Stanton Fine Furniture