When is it best to use kiln-dried vs. air-dried vs. green wood in a project?

Question

Kiln dried wood is usually recommended for woodworking projects since it's more stable than green and air dried lumber.

On the other hand, I've been told kiln dried wood is bad for lathe work, and in fact green wood is best for turning.

Air dried lumber seems to be considered workable but perhaps not ideal for anything.

Does this pretty much sum it up, or are there other applications such as carving in which a certain moisture level is ideal? Is there any case in which air-dried lumber is preferable over both kiln-dried and green wood?

Answer 1

Green — Very fun to turn and it's like shaping butter, however, the greener it is the more likely you will get cracks as it dries and quite possibly a bit of warping. for building projects (book shelves, tables buildings etc) Green is a terrible choice unless you are going for a specific affect as the wood dries.

Kiln (fast kiln) — Very dry and stable, good for building projects, harder on lathe chisels, and requires more sharpening. Kiln drying is also hard on the substructure of the wood damaging it and does not last as long as air dried (slow kiln) wood.

Air dry/slow kiln — Takes much longer to be at a usable moisture content for building projects, but for turning is much more stable than green and not as hard on the chisels. For furniture it is best because it doesn't have the damage caused by fast kiln drying and it will be much more stable than green wood.

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When I say fast kiln drying I'm referring to commercial systems that dry the lumber very fast (in a matter of hours).

Slow kiln drying refers to something like my solar kiln. It heats up during the day, releasing moisture. At night the moisture in the center of the wood has an opportunity to dissipate evenly throughout the wood. This results in a more even drying and puts less stress on the wood substructures. Most of my wood is air dried and then I finish it in my solar kiln to get it down to 10% (or less) moisture content.

Answer 2

This is exactly right. Kiln dried wood is typically prized for it's stability and use in construction. This may be preferable in pieces work that would get laminated or otherwise glued together, however if it is too dry, sometimes even the moisture from the glue can cause swelling and require extra drying time.

I typically prefer to turn in air dried wood. It tends to have the least amount of warping, especially if the cut ends were waxed or otherwise sealed. I typically worked with wood that had been dried slowly, with the bark still on. This was ideal for turning. With moisture just around 12% - 14% I was most comfortable.

Most large burls I know of are air dried, and then resawn into more manageable pieces.

However, there are techniques to turn green wood EXPECTING it to warp and twist, and doing it in such a way as to not crack. Those were the most beautiful, organic pieces.

There are pros and cons to all kinds of wood, but I find with patience and a steady hand are often the limiting factors compared to the moisture content. Each piece of wood should be selected for the application/project in mind.

I wish you good luck, and large piles of woodchips.