A check is a small crack that occurs in the end grain of the board or log. These checks can increase in size to form a crack. A crack is usually a grain separation within the grain. Any piece of wood will be checked as it dries. This is a natural occurrence, but it varies between tree species. Everyone will check; some more and some less.

From a piece of green wood (green wood is wet wood) the surface begins to dry out; as the wood dries, it shrinks; the wood fiber on the exterior of the wood dries at a different rate than the interior wood. As moisture evaporates from the wood, the outer faster and the inner slower, the outer wood shrinks, around the inner wood which is wetter and larger; so the outside will control as it shrinks around the wetter center wood. Left alone, these little checks will continue to grow and render the wood worthless or firewood.

There are several methods to prevent or slow down checks. To do so you have to slow down the evaporation process. One way is to coat the ends of the wood with wax (Anchor Seal is good), this will help, but not on all species. Does the local environment have much to do with the drying of the wood? Do you live in a cool and humid area or do you live in a warm and dry place?

The lumber can be cut into various sizes for future use and then stacked in a cool, dry place with good air circulation. There will be some checking and cracking with this method, but you can usually avoid them. This type of drying takes longer and requires more space.

The best way to dry wood is to use a kiln. This can be expensive, but the recovery of lumber from loss due to cracks and crevices is great, and the time required to have dry lumber ready to use on your project is a huge benefit. On a small scale, ovens are easy to build. They require an insulated box of a certain size, a fan for air circulation, a heat source, and a dehumidifier to remove moisture.

I recently built a small kiln in which I could dry 5-6 bowls which I turned into green wood. Most bowls take 7-10 days in the oven and I usually set them in a dry place and let them acclimate for about a week. A couple of technical tips. If the dehumidifier removes moisture quickly, the wood will crack, use an on/off timer. Moisture meters will not work. Weigh the wood every day, as the wood dries the change in weight will slow down. When the weight changes slightly from day to day or stops changing at all, the wood is dry. There will always be some amount of warping, so overcut the wood to remove the warp.

I always like to turn wood green. The small oven works very well for me.