air or kiln dried?

I'm in the process of reading about guitar building and getting the tools together to start building a few guitars. I will probably build an electric 6 string first since the level of difficulty looks somewhat less than an acoustic. Anyway, I have some figured walnut slabs drying right now that I'd like to use for my first build. I've only ever used air-dried lumber and haven't yet had the opportunity to run anything through a kiln, but looking at tone wood online it looks like everything is kiln dried.

So I have to ask - is there a benefit of kiln or air dried wood over the other when it comes to guitars?

Quote:

---

Originally Posted by Wes Ramsey

I'm in the process of reading about guitar building and getting the tools together to start building a few guitars. I will probably build an electric 6 string first since the level of difficulty looks somewhat less than an acoustic. Anyway, I have some figured walnut slabs drying right now that I'd like to use for my first build. I've only ever used air-dried lumber and haven't yet had the opportunity to run anything through a kiln, but looking at tone wood online it looks like everything is kiln dried.

So I have to ask - is there a benefit of kiln or air dried wood over the other when it comes to guitars?

---

Most kiln dried wood undergoes a sterilization cycle at the end of the kiln run. Heat sterilization is the only 100% effective way to ensure that any bugs, larvae or eggs are killed. That is one of the primary benefits of KD lumber.

Quote:

---

Originally Posted by Scott T Smith

Most kiln dried wood undergoes a sterilization cycle at the end of the kiln run. Heat sterilization is the only 100% effective way to ensure that any bugs, larvae or eggs are killed. That is one of the primary benefits of KD lumber.

---

That makes sense. I've heard that the wood has to be at 160 degrees for a certain length of time to kill powder post beetles, but there are other ways to combat them. They only lay eggs on wood with a rough surface and prefer starchy woods. I have found them all over my oak lumber and in pine and walnut sapwood, but I haven't found them much to speak of in walnut or pine heart wood. None in cherry. I haven't looked at my maple since I stacked it, but I bet I find some.

From what I understand, once the board has PPB bug holes there's a chance it will always have some in it, but if you can plane a fresh surface and get rid of the bug holes then they've been eliminated from that piece of wood. Until such time as they find it again :)

Anyway, I've only ever worked with air-dried lumber and would like to continue that direction into guitar building. What I'm wondering is if there's something that happens to the cellular structure of the wood during kiln drying that makes it more stable or enhances a tone wood's sound properties or makes it otherwise preferable for use in guitars.

Some people use a more extreme heating process than kiln drying called torrefaction to alter the properties of soundboards. It does alter the wood, and is supposed to make it more stable. I have never tried it though.

Not an expert and can't adress the "in a guitar" part. Kiln drying is sometimes described as removing the water IN the cells as well as between the cells. I've tested samples from ONE board that were air dried against pieces from SAME board that were kiln dried. Soaked them in water over several days then checked sizes, the KD did not swell ,the air dried did. After several cycles there was no difference. So I see the kiln drying as helping the stability in changing air conditions. And that is the thinking behind millwork standards specifying kiln dried,or a big part of it.

Wes, the information that you "heard" regarding the sterilization temperature of wood is incorrect.

USDA FPL specs require that the lumber be heated until the core of the lumber is 133F for at least 30 minutes. This will successfully sterilize the lumber, including killing any PPB eggs or larvae present. Woodworkers that air dry their own lumber can sterilize their lumber themselves at home using a space heater and some foam board. Christian Becksvoort had an article in FWW a few years back about this.

Mel, what you're referring to is known as "bound water" and "free water". Bound is what is trapped inside the cell walls, whereas free water is what is inside the cell itself. Shrinkage in wood occurs when the bound water is evacuated, which is towards the end of the drying cycle. Typically free water is removed first during the drying cycle. Once the free water is removed to below fiber saturation point (typically around 30% MC), the bound water starts being removed and the drying process becomes more difficult.

Most drying related defects occur during the initial stages of drying (and when the lumber is above 35% MC), but you don't see them visually under the lumber is below 25% MC because that's when the shrinkage makes the surface checks, etc visible to the naked eye.

Scott, thanks for clarification.

Not a huge amount of experience, but I have noticed that air dried lumber has better coloring than kiln dried. It almost seems that kiln dried has the colors washed out. Not the best description, but my perception.

Quote:

---

Originally Posted by Sean Hagerty

Not a huge amount of experience, but I have noticed that air dried lumber has better coloring than kiln dried. It almost seems that kiln dried has the colors washed out. Not the best description, but my perception.

---

I've always heard that, but again, I have almost zero experience working with kiln-dried wood.