Alcohol Soaking Q and A

I have answered many questions since publishing the alcohol drying process in November 2004. My intent here is to compile a collection Q & A to make it easier for people to understand the process.

The following 4 questions were asked by Greg in an email dated 12/04/2005

Q: Does the alcohol itself take on water as the bowl takes on alcohol? Meaning do they exchange liquids?
A: Yes, water and alcohol are miscible. The water in the wood and the alcohol in the container will exchange until they are at equilibrium.

Q: Does alcohol retard mold, staining etc.?
A: Alcohol in high enough concentration will kill most organisms. The same process that causes alcohol to achieve equilibrium with water in wood will essentially dehydrate an organism which isn't good for it. Once the alcohol evaporates new organisms can colonize the surface of the wood. Some people speculate that natural mold inhibitors in wood are destroyed by soaking in alcohol or boiling. This is not something I am inclined to delve into since the alcohol process drys pieces in a short time making the wood too dry for most organisms to flourish.

Q: Does the alcohol lose strength with use?
A: Yes, alcohol concentration in the soaking solution will decrease over time. In my initial testing I used fairly small pieces in a small container. I added alcohol as the level in the container decreased which kept the concentration from drooping too low. I have done some tracking of alcohol concentration recently to identify a lower limit in which the process is effective. I hope to have more on that soon.

Q: I currently boil per Steve Russel's method. ...Would you recommend alcohol soaking over boiling? It would be much easier to throw bowls in a large container rather than boiling.
A: I am familiar with Steve Russel's method. Steve has done a lot of work developing the boiling process and has freely shared his information with the turning world. I used boiling for a while but it is inconvenient especially if you are only doing an occasional turning. Also, boiling does not speed the drying process. One of my goals was to devise a passive method for improving the bowl drying process. Just drop the piece in a bucket of alcohol and take it out the next day or next week if you want. I haven’t boiled a bowl in over three years so you can conclude that I recommend alcohol soaking over boiling.

A few more questions from Greg in an email dated 12/08/2005

Q: With the alcohol soak method is the tendency of the wood to distort diminished, if so, how much?
A: Bowls do not distort as much when soaked in alcohol before drying. It is counter intuitive to think thinner walls result in less distortion. I found it to be true when I started testing the process.

Q: Do I ignore the 10%wall thickness rule?
A: I don't use the 10% rule with alcohol soaking. When I started the testing process instead of starting with the 10% rule of thumb I started at 1/2" which I thought was extremely thin. It turns out that 1/2" is usually a good thickness for up to 8" bowls. I usually turn small bowls to 3/8" thickness and finish turn to about 1/4". There are a lot of factors in bowl distortion so my wall thickness recommendation are just an other rule of thumb.

Q: Once the bowl is dry is there any odor from the booze and will polymerized tung oil be compatible as a finish?
A: Alcohol will completely vaporize and leave no odor. There will be no problem with any finish you use on the dry wood. Most people forget that shellac is thinned with denatured alcohol and once the alcohol evaporates the finish is food safe.

Richard Dowling asked this via email on 1/3/06.

Q: "I picked up some Madrone in California last week. It's very green. Do you have any experience turning it?"

A: My experience with madrona is that it needs to be turned thinner than the 10% rule. Also, use fresh alcohol and soak the roughed out bowl at least 24 hours. I had some spectacular failures when I left the walls too thick and soaked them in an old solution that had a low percentage of alcohol. Subsequent pieces that were turned thinners and soaked in fresh alcohol had very few problems.

Madrona needs to be turned soon after cutting. It splits every which way you can imagine. It needs to be sealed on all surfaces and kept out of drafts and sunlight. Madrona is also susceptible to blue stain which will develop in the sealed blanks.

Questions from Barb and Mike Hays. Email dated 2/26/06.

Please let us know about how long to soak 10 pen blanks taped together. Green maple.

The following answers assume the wood in question is straight grained with no defects.

Q: How long do we soak them?
A: Seperate the blanks before placing in alcohol. Soak them over night or about 8 hours.

Q: Then what do we do with them?
A: After removing them from the alcohol set the blanks on a rack and let the surface dry. It takes about an hour. Once the surface is relatively dry, coat the ends with an end grain sealer. Coat the sides about 1/2" from the end. Leave the rest of the blank unsealed. Place the coated blanks on a rack. It take between one to two weeks for the blanks to stabilize. I cut pen blanks from 1/2" to 1" square with lengths from 4 1/2" to 6".

An alternative to sealing the end grain after soaking in alcohol is to put the blanks in a paper bag and close the opening. This method leads to more end grain checks and extends the drying time. However, it is expedient when generating large numbers of small blanks.

We enjoyed your program at the Olympia woodturners meeting last month.

Barb and Mike Hays

Questions from Terry Bourk.
Email dated 2/26/06.

Q: Is there some reason why you don't give the composition of the DNA sold by Home Depot on your blog??

A: I have listed the brands of DNA that are mostly ethanol. Klean-Strip SLX
brand is about 45% ethanol and over 50% methanol. I also miss read the MSDS for SLX brand DNA. After someone on WoodCentral commented on the deception I took a closer look. That is when I put the info on my blog about brands that have high ethanol content.

Question from Michael Stadulis
Email dated 6/13/2006

Q: Maybe you've written this someplace, but I'm curious if you have any empirical data about how much less warpage you get this way(alcohol drying process)....?

A: When I began investigating methods for shortening the drying process I decided trying to quantify warpage was going to be very difficult. I decided the easiest way was a go, no go test. Can I turn a finished bowl from the dried piece? As you may guess nearly every piece passed the test. A while back I began measuring the maximum thickness I could turn from a dried bowl. What I do is retrue the rim of the bowl and then scribe the largest and smallest circles and measure the difference. From the small amount of data I have gathered a bowl roughed to 5/8" will yield a finished piece with wall thickness of about 7/16". I abandoned making control pieces early in the experiment because I was not writing a Masters Thesis. I just continued with what worked and used it.

Question from Suzanne
Comment dated 10/21/2010

Q: I have some fresh walnut blanks that are 3" x 3" x 11". Do you think there's any chance of drying them using your DNA method?

A: Yes, it is possible to dry the turning squares using the DNA method. Soak the squares in denatured alcohol over night. Remove and coat the ends and about 1/2" of the sides with end grain sealer or wax. Stand the pieces on end and allow to dry. Although I can't prove it helps the drying process, I flip the squares end for end each time I weigh them. Walnut is a porous wood and will dry fairly quickly.

Question from Anonymous
Comment dated 12/25/2010

Q: David, when we pull our blanks from the DNA and begin drying them...what are we removing during the drying process? Are we removing water, or has most of the water in the bowl been replaced with DNA, and we are now waiting for the DNA to migrate to the surface, to evaporate off?

A: When the bowl is submerged in alcohol water in the wood will exchange with alcohol in the solution until an equilibrium is reached. When the bowl is removed from the solution alcohol will evaporate quicker than water because of a higher vapor pressure.

Question from Dora
Comment posted 11/25/2010

Q: I design jewelry in wax, and I am interested in locating pure solvent alcohol for heating the instruments I use. I have not had much luck finding it lately. I have only been able to find denatured alcohol. Unfortunately, this type of alcohol emits a strong odor and smoke and leaves an oily residue. I was wondering if you have an idea of where I could locate the pure solvent alcohol. I would appreciate any information you can provide me. By the way, I live in Houston, Texas.

A: Pure ethanol is Everclear liquor and is highly taxed. Find a brand of denatured alcohol that has a high ethanol content of 90%. Three brands I am familiar with are Parks, True Value and Sunnyside.

Question from Anonymous
Comment dated 01/19/2011

Q: You mentioned that you also tried isopropyll alcohol, but didn't like its smell. I can get isopropyll alcohol that is 99% alcohol....better than denatured. Does the smell finally leave the wood, like denatured does?

A: I did not pursue drying bowls using isopropyl alcohol. A few people reported satisfactory results using isopropyl alcohol. Remember isopropyl alcohol is poisonous. Consult the manufacture's MSDS for precautions when using isopropyl alcohol.

The odor did disipate which is to be expected since isopropyl alcohol has a high vapor pressure. If you do use isopropyl alcohol for drying bowls please notify me of your results so I can share your finding with others.