Green wood drying

[Bernie Kopfer]

Living in NC Washington is wonderful, but we are dry! I keep the shop around 80*with AC and the inside humidity is usually 35-45% and lower, since outside is often much less. Wood dries quickly to about 6%. My usual technique is to green turn, coat with PVA and when dry, weigh and place in a brown paper bag to slow down moisture loss even more. Weigh every two-three weeks; usually, unless very thick, it is stable in less than three months. I put multiple pieces in a bag.
I'm wondering if there is a percentage moisture content of the wood below which I can safely just let the bowls finish drying on the shelf w/o the bags? The bags are a pain and I would like them to be gone as soon as reasonable. The green wood usually starts at about 25%

[Prashun Patel]

Interesting you start that "low". A lot of my green wood starts in the high 30's. Maybe my meter isn't calibrated.

I never use bags. If you are sealing the ends, I am not sure you need them. When I have used them, I have never kept them in bags for more than a week or two. And even then I'm not convinced it does anything. My drying shelf is very near the floor in my basement where there isn't a ton of air flow.

I am surprised you get stability after 3 months. On roughouts between 3/4" and 1.25" thick, I usually need at least 9 months.

[Bernie Kopfer]

Interesting you start that "low". A lot of my green wood starts in the high 30's. Maybe my meter isn't calibrated.

I never use bags. If you are sealing the ends, I am not sure you need them. When I have used them, I have never kept them in bags for more than a week or two. And even then I'm not convinced it does anything. My drying shelf is very near the floor in my basement where there isn't a ton of air flow.

I am surprised you get stability after 3 months. On roughouts between 3/4" and 1.25" thick, I usually need at least 9 months.

My cheapie meter tops out at 25%. But yes with our heat and super low humidity wood dries very quickly. Back in the recesses of my memory I remember someone saying that after wood drops to 15% there is no need to worry about cracks starting. Trying to find out if that is true or not.

[Richard Coers]

I agree with Patel. I'm skeptical that the wood is at 25% after rough turning. I've also never heard of air dried wood dropping to 6%. Usually you have to collapse some cell walls to get the bound water out of the wood. And that is always done in a kiln. You also say nothing about the species, size, and wall thickness of your bowls, so I will not make a guess at when to bring it out of the bag. Ash or Walnut can be treated much differently than fruit woods.

[Thomas Wilson80]

FWIW, I am in central utah and it is also very hot and dry here - I rough turn and then coat the entire bowl with anchorseal and store in a basement cold storage room. I’ve never used bags and haven’t had any cracks in the 15 or so rough-turned bowls I’ve done in the last year (mostly various elm, sycamore, and poplar). I should add that many of the first ones I cored have somewhat thick and a little uneven walls, but maybe it’s the species. Haven’t gotten any large fruit wood or other crack-prone species to try yet!
TOM

[Bernie Kopfer]

So I went out to the shop took out my Timbercheck pinned moisture meter and stared measuring some bowls that I green turned in the last 6months. Fruit cherry, birch, locust, Russian olive, wanut and maple. And some 2X lumber that’s been around a while. All IF the weight is stable measure at 6% those almost stable 8-10% . I try as much as possible to turn thickness to the 10% rule. More for cherry and birch.
So back to my question,does anybody know if there is a moisture % at which most drying wood stops developing new cracks? I realize that this is very subjective, but combined experiences are often the best we have.

[Richard Coers]

In most areas, it's hard to crack most species when they are below 20%. But I have no idea about the desert area you live in. I would be skeptical of any advice unless they live or have lived in your type of climate. I declare you as the expert. LOL

[Neil Strong]

So back to my question,does anybody know if there is a moisture % at which most drying wood stops developing new cracks? I realize that this is very subjective, but combined experiences are often the best we have.

It depends on the species. You just have to get to know your particular woods.

I have a number of moisture meters calibrated against each other and my pre-turned pieces can get down to 5-6% at the end of our long hot dry summers, but then start to suck up the moisture from the air during our cool wet winters and can then get up to 18% again by the end of winter. So, in my case I open stack anything below 20%.

I don't have aircon in my workshops and they are not tightly sealed. I have has some pieces develop a large crack for the first time after 10 years of going through that cycle. For me its just not worth the effort of going to any extra effort to prevent that happening... I expect a % loss.

[Don Stephan]

As soon as I finish a once-turned bowl, I note the weight in grams on the tenon, and place in a paper bag on the concrete floor (on grade). I weight every friday, and when the weight loss from the prior week is less than 2% I move the bowl in the bag onto a table top and continue weighing weekly. When the weight loss from the prior week is again less than 2% I remove the bag, leaving the uncovered bowl on the table top and continue weighing weekly. When the weight loss from the prior week again is less than 2% I consider the bowl dry to ambient conditions and ready for sanding and finish. Perhaps 1 in 10 bowls will develop a crack, most small and easily filled with tinted epoxy. I do not turn twice turned bowls, or apply sealer to once turned bowls.