DNA Questions

[Tony Bilello]

I mentioned earlier on other posts that I havent done any turning in about 18 years.

I recently purchased a Jet 1236 lathe and am rearing to go.
Until I joined this group a few days ago, I had never heard of DNA treatments to turnings.
I understand that the alcohol and the moisture in the wood tend to want to equalize and a good part of the water moisture in the wood is now displaced with an alcohol/water mixture that dries quicker. I'm OK to this much.
Where I get lost is the fact that this makes the wood dry quicker. How does this reduce cracking and splitting? The wood is still drying, I dont understand.
It is still shrinking and creating stresses all be it quicker than normal, but still shrinking. What dont I understand?

Tony B

[Richard Madison]

Good question Tony.

[Brian Brown]

From the way I understand it, the DNA is just to speed the drying process for those of us with no patience. How you handle and store the wood after will reduce the checking and cracking. Wrap the outside of the rough cut tightly in newspaper. leaving the interior exposed to air. Then, put the whole bundle in a largish (approx. 4X the size of rough out) paper bag, and close the top, leaving air space around the whole bundle. Fold the top over and clamp/staple to prevent air from getting in. The theory is that the evaporation of water will raise the humidity in the bag, and slow the drying so that the different depths of wood dry at more or less the same rate. Leaving the interior of the rough out exposed, makes the interior dry a bit faster than the outside., giving some pressure form the inside reducing the cracking. Great theory. Sometimes it even works.:rolleyes:

[Steve Schlumpf]

Tony - check out this webpage on the DNA process. Lots of info there!

http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=turning&file=articles_473.shtml

The method of wrapping the blank after soaking has a lot to do with it's success of drying and not cracking. The above article states "The reason for wrapping the outside only is the theory that it will create a compressive stress on the bowl by drying the inside quicker than the outside. As the inside dries it shrinks which pulls on the outside causing it to compress. This compressive force minimizes cracking during the drying process. Thinner walls yields less distortion and fewer cracks by decreasing the maximum stress developed between the inside and the outside."

Hope this helps answer some of your questions.

[Tony Bilello]

BTW, thanks for the info and the link.
I read the article by Dave Smith and it is quite impressive. I'm glad to know that I can purchase DNA easily and not have to dip into my rum.
Anyway, this leads to my next question......What if I like the warping and movement of the wood. I too am warped.
Can I turn a bowl to its final thickness and shape, put it in DNA for a few days and follow the drying procedure for several weeks then let it dry out completely and apply the finish?
This is what I would like to do with natural edge bowls. Would it help?
Way back when i used to turn, that was a normal thing to turn green wood, finish it on the lathe and hope for the best. Most survived, but not all. I also remember putting green bowls in the mico-wave. Never had much luck with that. Would this DNA procedure decrease the death toll?

Tony B

[Darryl Hansen]

yes. Natural edge bowls do well in DNA and after they dry will take on a shape that is very pleasing. I have used on cherry, walnut, oak, beech and other woods both green and dry. Liquid soap has not worked quite as well for me although the sanding is easier.

[Ralph Lindberg]

Tony

DNA is one of the "hot topics"; some claim it works gang-busters, others that it doesn't work at all.

People that I know, and trust, like Reed (Robo Hippy) and Fred Holder (More Woodworking) have done true blind tests (using wood, from the same tree) and found no impact on drying time/weight.

Others have found just the opposite.

I once had a chance to talk to an industry "person" (ie commercial wood drying, at lumber mills) about this. He had actually read about studies the industry had done. The results of those studies showed that the results can be unpredictable. Sometimes it worked, sometimes not.

I also have seen some University studies on using DNA, only in this case it was just one step in a program of using different treatments (each with a lower EV point), to displace all the water in water-logged wood items (they were recovering soaked wooden "finds")

People I know, and trust, (like Steve Russell) have done true blind studies on boiling blanks and found that this method does, consistently work and reduce the failure rate and (slightly) shorten drying time.

Microwaving also works, BUT… Drying the wood too fast is going go cause issues. Personally I never go more the 30 to 60 seconds of full power and let the rough-out rest for at least 30 minutes. If the wood is really wet, I keep the time short, and place it in a paper bag, filled with wood-chips during the “between” periods. I also store the rough-out in that bag, if I am not engaged in a drying cycle. My success rate is VERY good (even on fruit woods).

But I also use boiling, especially on tropical woods

[Reed Gray]

Thanks Ralph. I do turn thin, to final thickness, and then let them dry and warp, and have noticed no difference in drying rates, movement, or lack of cracking. I haven't tried the soaking methods on thick turned green bowls that are to be returned later. There could be a difference, but that is an experiment for 'when I get around to it'. I do need to try the paper on the outside method. Mostly, it is fairly humid and cool here in Oregon, so drying isn't too much of a problem. I start them off on the floor for a few days, and then up on a wire rack for a few more days. A 1/4 inch thick bowl will reach equilibrium (as dry as it will get) in a week to 10 days. Boiling is a solution for difficult woods, but like soaking in a water barrel for a year or so, it muddles the colors, and I don't like the end result. The soap soak really does make sanding easier.
robo hippy