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Dna
- Thread starter dan1908
- Start date
Dan,
Here is a link to an article on DNA drying procedure. It was written by Dave Smith who is the developer of the process. Dave also has a blog dealing with his process which may add some more information.
http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=turning&file=articles_473.shtml
Here is a link to an article on DNA drying procedure. It was written by Dave Smith who is the developer of the process. Dave also has a blog dealing with his process which may add some more information.
http://www.woodcentral.com/cgi-bin/readarticle.pl?dir=turning&file=articles_473.shtml
Dan:
Have a read also at:
http://alcoholsoaking.blogspot.com/
In my experience it does help speed the drying process considerably. I use it routinely with bowls and vessels that were turned wet which are small enough to fit into my alcohol 'vat'. It also has a benefit of stopping the spalting process immediately if one is wet-turning "living" spalted wood where the fungi are likely still alive.
As to "how it works" (or perhaps more accurately, why it works) this has not been adequately tested to isolate one or more specific variables, however some prevailing hypotheses are that by replacing (or, better, diluting) the water with a solvent that has a lower boiling point (hence a lower vapor point), the evaporation of the liquid mixture in the wood takes place more rapidly with an ethanolic solution than it would with water alone. Ethanol may also interact with the cell walls and/or the extractives found in the wood and further increase the rate that water is given-up during the drying process.
You might want to have a look at several other methods of drying green wood to get an idea of the range of possibilities, and what the pros and cons are for each method. Links for explanations of these methods can be found at:
http://rwallace.public.iastate.edu/WTlinks.html#Processing-Toxic-Woods
(Scroll down to the 'Drying Techniques' section to learn more about these methods.)
Good luck!!
Rob Wallace
Have a read also at:
http://alcoholsoaking.blogspot.com/
In my experience it does help speed the drying process considerably. I use it routinely with bowls and vessels that were turned wet which are small enough to fit into my alcohol 'vat'. It also has a benefit of stopping the spalting process immediately if one is wet-turning "living" spalted wood where the fungi are likely still alive.
As to "how it works" (or perhaps more accurately, why it works) this has not been adequately tested to isolate one or more specific variables, however some prevailing hypotheses are that by replacing (or, better, diluting) the water with a solvent that has a lower boiling point (hence a lower vapor point), the evaporation of the liquid mixture in the wood takes place more rapidly with an ethanolic solution than it would with water alone. Ethanol may also interact with the cell walls and/or the extractives found in the wood and further increase the rate that water is given-up during the drying process.
You might want to have a look at several other methods of drying green wood to get an idea of the range of possibilities, and what the pros and cons are for each method. Links for explanations of these methods can be found at:
http://rwallace.public.iastate.edu/WTlinks.html#Processing-Toxic-Woods
(Scroll down to the 'Drying Techniques' section to learn more about these methods.)
Good luck!!
Rob Wallace
Dan
Good questions, unfortunately few real answers. Wood turners have done some studies, not all of them showed it worked.
There also have been some studies in Academia. Texas A&M University did one. But you will note that they were not interested in drying green (wet) wood, but rather water soaked items that need preservation.
I also once had the opportunity to talk to a Professional in the lumber mil industry that was familiar with Industry experiments done in the field. In a nutshell: They were unable to accurately predict the results:
On my Round-To-It list is contacting the USFS to inquire if they have anything published.
Good questions, unfortunately few real answers. Wood turners have done some studies, not all of them showed it worked.
There also have been some studies in Academia. Texas A&M University did one. But you will note that they were not interested in drying green (wet) wood, but rather water soaked items that need preservation.
I also once had the opportunity to talk to a Professional in the lumber mil industry that was familiar with Industry experiments done in the field. In a nutshell: They were unable to accurately predict the results:
- it was not predictable, that is, different trees of the same specie, grown under similar conditions behaved differently
- Sometimes different parts of the same tree behaved differently
- It was more costly then other systems (kiln, microwave, etc)
On my Round-To-It list is contacting the USFS to inquire if they have anything published.
After reading about a test that Fred Holder (More Woodturning Magazine) did on DNA drying compared to air drying, I tried a test also. I took 3 bowl sets (6 total from coring, and from the same log sections) turned them to final thickness, about 1/4 inch, and dried them. One set was DNA soaked, one set was LDD (liquid dishwashing detergent) soaked, and the other was air dried. I would weigh them daily on a gram scale to see how long it took them to reach equilibrium. They all dried in the exact same amount of time. There was no difference in how much they moved. After drying several hundred bowls in the DNA, more air dried, and a couple thousand in LDD, the only real difference I can tell, is that the DNA soaked ones are harder to sand out, and the LDD ones are a lot easier to sand out. There is no difference in how much they move, or how well they dry without cracking. This is why I continue to LDD soak. Anything to help sanding.
The results could be different if you turn thick, soak, dry and then return, but I have never tried this. Some day I would like to try a more thurough test with different woods and different thicknesses.
robo hippy
The results could be different if you turn thick, soak, dry and then return, but I have never tried this. Some day I would like to try a more thurough test with different woods and different thicknesses.
robo hippy
I'll contribute the obligatory safety notice:
If you do decide to experiment/use DNA, be sure to do it in a well ventilated area away from open flames or other ignition sources!
I have a basement shop where the furnace is, and the prospect of knocking over a vat full of DNA under my home makes it a no-brainer that this is not an option for me (plus at hobbiest levels, the DNA would be evaporated before I could soak 5 bowls!)
If you do decide to experiment/use DNA, be sure to do it in a well ventilated area away from open flames or other ignition sources!
I have a basement shop where the furnace is, and the prospect of knocking over a vat full of DNA under my home makes it a no-brainer that this is not an option for me (plus at hobbiest levels, the DNA would be evaporated before I could soak 5 bowls!)
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Can't. Experiment shows it doesn't. Consider that the reason we are able to get alcohol above the poisonous (to the yeast producing it) 15% level is because alcohol evaporates faster than the water that dilutes it. It's called distillation.
As to stabilization or "replacement" of water in the wood, ask why we don't lose the potency of our potables by storing them in wood as we have for centuries. The old wine barrels shrink and warp just like fresh wood, don't they?
When you go to Dave's site, note that he makes no comparison to a control, merely suggests that the straw man of "an inch per year" has been vanquished. Documentation of evaporation isn't much real use.
Guaranteed, if it were a viable process, it would be used commercially.
Dan, after the twin hurricanes of 2004 I spent the better part of the next 6 months salvaging various woods from trees destroyed by the storms. I tried the DNA soak and found that while it did not seem to cause any appreciably faster drying, it did seem to limit the amount of warping of the rough turned bowls.
I also read through the experiments done by A & M and was impressed that they had spent so much money and time to evaluate various solvents. For someone to say that it is impossible for DNA to speed drying of green wood, they should read carefully about all these preservation trials and experiments.
Personally, I do believe that not every wood reacts the same way under the same circumstances. It depends on where you are and the natural environment. All you can do is experiment and see how it works for you.
I compared the DNA drying to paper bags full of wood shavings as far as weight loss. Very little difference, but that could be because of the higher humidity in Florida. But the DNA assisted bowls warped much less and had no major cracks. Good Luck! And keep turning and learning.
I also read through the experiments done by A & M and was impressed that they had spent so much money and time to evaluate various solvents. For someone to say that it is impossible for DNA to speed drying of green wood, they should read carefully about all these preservation trials and experiments.
Personally, I do believe that not every wood reacts the same way under the same circumstances. It depends on where you are and the natural environment. All you can do is experiment and see how it works for you.
I compared the DNA drying to paper bags full of wood shavings as far as weight loss. Very little difference, but that could be because of the higher humidity in Florida. But the DNA assisted bowls warped much less and had no major cracks. Good Luck! And keep turning and learning.
My own experience parallels that outlined by "elderbarryl" above. No double blind studies here (I ain't runnin' a test lab) but I have noticed a subtle difference. That said, I can't say that the "subtle" difference is worthy of the investment necessary to engage in a DNA drying process as compared to other methods. All things considered, I don't use the DNA method any longer.
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Difficult to believe you could draw such conclusions from the article here. http://nautarch.tamu.edu/class/anth605/File6.htm
Note the terms "series" or "succession" of alcohol baths and the soak times and concentrations. This is simple dilution, as would be accomplished by mixing black and white sand, withdrawing part of the mixture, then mixing more black, discarding, and so forth to achieve a predominant black. The method used for dehydrating histological specimens in preparation for slides is similarly a process of dilution, involving successive baths, as those who took the lab may recall.
Immersion in a miscible liquid is the equivalent of enclosing the piece in a tight plastic bag. It will produce saturated air surrounding the piece which will stop water loss, as it has nowhere to go. Instead expose the piece to open air and decreasing levels of relative humidity where the saturated air is drawn off successively, as in a dry kiln. Air has a much lower vapor pressure than any liquid, thus allowing more rapid loss, even when the molecules are not provided extra energy to break the hydrogen bonds by addition of heat. Vacuum kilns lower the total pressure to achieve the same effect, and the saturated air is drawn off successively to allow for further loss.
Note the processes used involving liquids of lower vapor pressure (higher boiling points) than water, including PEG, where the material, though miscible with water, is actually a semi-solid at the temperatures and pressures normally encountered by the piece. These are quite successful in maintaining the bulk of the wood and minimizing distortion. Where alcohol is used, it is used as a solvent for solids or semi-solids not normally miscible with water, as in the resin or camphor methods, to accomplish the same "bulking."
Control of the relative humidity is the answer to the problem of drying. Control of distortion is accomplished by thin sections and careful reading of, and allowances for, orientation of the annual rings.
Is it possible that the DNA assisted bowls warped and cracked less while drying because they didn't really finish drying? Just because they stopped losing weght over your measurement interval wouldn't necessarily mean they were "dry". It would be interesting to compare a DNA bowl with a non-DNA bowl a year or two after finish turning and see if there was any difference in additional warping.
In high humidity areas, how long do you think it would take for the alcohol level in the tub to drop to virtually nil? Alcohol will absorb water from the air in addition to any wood that's dumped in it. The alcholol will also evaporate. The two will result in more water and less alcohol in the tub over time.
I wonder if the DNA proponents would get the same benefits by soaking their rough out in POW (plain old water). Might want to give it a try. If it works just as good as DNA it would be a lot cheaper and safer.
Ed
In high humidity areas, how long do you think it would take for the alcohol level in the tub to drop to virtually nil? Alcohol will absorb water from the air in addition to any wood that's dumped in it. The alcholol will also evaporate. The two will result in more water and less alcohol in the tub over time.
I wonder if the DNA proponents would get the same benefits by soaking their rough out in POW (plain old water). Might want to give it a try. If it works just as good as DNA it would be a lot cheaper and safer.
Ed