LDD and an Australian technique

Interesting thought, but, as you know, the resins are not soluble in polar solvents like water. Addition of Sodium Tetraborate, a surfactant (detergent), in sufficient quantity may increase the solubility of resins and other semi-soluble extractives in the wood, but these have nothing to do with bound moisture. Loss of moisture bound by the cellulose and hemicelluloses is what causes the wood to shrink. Where the forces of shrinkage exceed the binding force of lignin, cracks appear.

The reason sawmills keep logs wet is - to keep them from uncontrolled drying. If the wood were not kept fully hydrated where vulnerable to evaporative forces, local fiber shrinkage could degrade the resulting timber by causing checks, which can grow into cracks. What the turners want to do is to get rid of the bound water at a rate which will keep the surface at the fiber saturation point by allowing capillary draw of unbound water from the interior. This is accomplished by control of the relative humidity around the piece - immersion is 100%, so no bound water will be lost. Relative humidity correlates directly to moisture content in wood, because the rate of loss depends on the ability of the surrounding air to take on water.

Which brings us to the realities of drying.

1) No shrinkage above the FSP. Free fall to ~30% moisture by weight, regardless of how rapid, won't degrade the piece, as long as the rate of loss from the surface is controlled. 2) Shrinkage is proportional and localized, depending on the orientation of the early/late wood and the total section. 3) Water is lost from end grain at ten times or more the rate of face grain loss.

We use these principles all the time. Spinning a piece to throw unbound moisture will not result in end checks - rather the opposite, as the water runs as a liquid from the surface. Gets us to the FSP much more rapidly. Some even blast compressed air from the inside to get even more out than centrifugal force can.

Cutting thinner allows more rapid drying with less visible distortion because there is less section to distort, and less distance for the moisture to reach open air. Eight percent of an inch is more than eight percent of a half inch, and less contiguous section throughout means that there is also less solid wood to pull against.

Weighing a piece as it dries will show the inapplicability of the "inch per year" rule of thumb used by people for air drying planks. In my basement, an inch thick hard maple bowl will reach equilibrium with a summer RH of ~70% within four to six weeks, because a bowl turned across the wood has no place more than an inch and a half from open air along end grain.

So, no magic needed, just control of RH. If you want to develop a schedule for drying like they use in a kiln, you will measure the same thing they do - relative humidity.

Oh yes, soap is not a detergent, and the effect of LDD, minimal as it is, is likely the result of the hygroscopic action of the glycol on the surface, not the surfactant.

Good information on drying at

Chapters two and three are especially pertinent.

George,

I knew that!

Still - tell me how your bowls dry at 70% RH in your basement? I thought we were striving for under 20% to be called "cured"/"dry"? At least, less than

40% as my central A/C house is presently at 37% while the outside earlier was 87%. And I keep a dehumidifier in my basement with the understanding that I want around 50% same as I'd like to have in the crawl space under the rest of the house. Now all of this is my "understanding" as in researched but not "researched".

Joe Ruminski, a North Carolina professional turner, uses a simple wood box lined with that styrofoam insulation stuff with a dehumidifier and circulating fan in it; measures the water discharged to help judge progress without opening the box so much; and uses an electronic humidity probe for final testing. Has an electrical timer to control how often the dehumidifier is on so as to control the rate of drying. Without checking, I recall he was after less than 20%.

Since kiln-dried lumber gets wet without damage I suspect once having achieved a low level of moisture a "set" is taken by the wood that requires considerable moisture exposure to cause a difference later on.

Your soluability reasoning makes sense to me yet we have a strong contingent that believes soaking the wood helps (which doesn't seem to make sense). Unless the key isn't drying but controlling the rate of change and/or the resultant composition of the wood, i.e. looking to stop checking instead of trying for the stability of "dried".

While I was ribbing you about the detail of your comments I need to say how much I appreciate the expertise involved and your willingness to share.

TomNie

You'll want to look at the FPL material I referenced for those answers. There you'll find a table showing relative humidity versus EMC. A 70% RH translates to ~13% moisture by weight at 68F. At "normal" RH of 50, and the standard 20C, wood will contain about 9% moisture by weight.

In reality, of course, we can regulate the RH around our pieces a lot of different ways, ranging from waxed ends to full containers. They even create their own envelope of elevated RH if you leave them in an area with poor air circulation.

Soaking in (X) is the Philosopher's Stone that takes that piece with full crotch figure and pith included and changes it into a display piece at the best gallery in town. Unfortunately, it continues to be elusive. Until that day when success rates rise above pure chance and are demonstrated to have occurred as a _result_ of an independent variable, soaking something to dry it will make as much sense as fighting for peace.