Drying time

[Ken Glass]

Hey Gang,
Is there a rule of thumb on drying time for green roughed out bowl blanks. I have 5 or 6 wrapped in brown paper, (with chips) drying for several days. These were submerged in DNA for 24 hours and set out to dry for an hour and then wrapped with chips from the rough out. I have been recording the weight for two weeks on some of the larger bowls. They were steadily losing weight daily, but have virtually stopped losing the last few days. The smallest ones stopped losing the fastest. One turning even gained a couple ounces for a day or two, then has stayed the same. The question is: Do you have a certain time frame for drying or do you use the weight loss method to determine when you finish turn the piece? If you use the weight loss method, how long after the bowl stops losing weight do you consider it dry enough to finish without warping?

[David Walser]

Ken,

I've seen estimates based on the thickness of the wood, but my experience is that it depends on a lot of other factors. When I worked in a furniture mill, we wanted our wood (all 2"x10" dimensional lumber) to be below 12% moisture before it was cut up into parts. When it arrived from the lumber mill, the wood typically had a moisture content of about 25%. Stickered inside the mill, it would typically take 3 - 4 weeks for the moisture content to drop to the desired level. However, sometimes the wood would dry out in less than a week and, once, I recall it took more than two months for the lumber to dry (we almost had to shut the mill down for lack of dry wood). My point (besides a love for the sound of my own typing) is that there were huge variations in the drying time for dimensional lumber inside the same building. Imagine how much the "average" drying time must vary when were talking about different parts of the country, different times of the year, different types of wood, different thicknesses, different shapes, different amounts of air movement, and different storage methods! Ignoring those differences, I'd say your bowls should dry out in about 6.5 days -- at least they would here in Mesa, Arizona. YMMV.

[Steve Schlumpf]

Ken - probably not a direct answer to your question of how long does it take - but you stated you wrap your bowls in brown paper with the rough out chips. After I take mine out of the DNA and dry - I wrap in brown paper bag only. I would think that adding the rough out chips would reintroduce moisture to the very wood I am trying to eliminate it from. Don't know - just seems that way to me.

Once the bowls are wrapped, they go on the shelf and are ready to turn in about a month or so. But the temperatures here are cool and the humidity is usually fairly high as I live 1/2 mile form Lake Superior so your drying time will be different.

Usually I spend summers cutting wood and turning blanks. By the end of fall I have all the wood cut, all the blanks roughed out and can start turning the rough outs that I had turned back in June. By the time I am finished turning all the rough outs - it is time to start cutting trees again!

I'm sure that helped you out tremendously!

[Ken Glass]

Steve,
I started adding chips when my last Hollow Form cracked so badly after the DNA bath and a few days in paper bags only. You might remember it was called the "Folgers Burst." From that point on, I started adding chips to slow the drying process. It has worked well, but most of the blanks have been under 6-8" in diameter. I now have a 14" bowl drying and several others in the 12" range. They, of course, lose more weight daily than the smaller bowls, but there doesn't seem to be a proportional rate of loss. I'm sure the moisture amount and type of green wood has much to do with that. Let me give you an example: I started a Heritage Birch bowl roughed out and DNA'd for 24 hours with the weight at 14lb 6 oz, wrapped in chips and in brown paper. It lost 1 lb the first day and every day for 5 days. Then the second week it lost 6-8 oz daily for 4-5 days. That's two weeks now and it is losing 1-2 oz a day. At what point would it be ready to turn. I am sure it will continue to lose in my dry basement shop, but my only wish is to keep it from warping badly after finish turning. I have a moisture meter, but I didn't think it would be worth while to record moisture from start to finish, since I don't know at what moisture level would be best. I do know in (dare I say flat work) I want it at between 6-8%. I believe that when it stops losing for 3 consecutive days I should be able to turn it to finish. Would you agree with that?

[charlie knighton]

you may still get some cracking, but you should only add dry chips, not chips that are freshly turned, i sort of keep a pile on the other side of the lathe :D

[Bernie Weishapl]

Ken most of my green woods are soaked a minimum of 48 hrs to a week. I found fruit wood soaked for a week stays pretty much crack free. I wrap mine like Steve with just a brown paper grocery sack. With bowls I cut a opening in the dished out portion of the bowl and sit it upside down on a cooling rack in a room that the temp is cool and not a whole lot of air flow. Lidded boxes I wrap but leave both ends open. I haven't had many problems so far. If I soak a bowl for say 72 hrs, flash dry it for 20 minutes and then wrap it generally takes about 3 weeks to be totally dry. Just my experience as we are rather dry here in Kansas.