Drying huge roughed blanks, using DNA

[dirk martin]

I'm told that if I'm going to rough out some large blanks (20 - 28 inches in diameter) that I should leave the walls a good 2" thick as it dries.

I plan on trying the Denatured Alcohol method for drying.

Anyone have any experience if DNA will work on 2" thick roughed blanks?
How long do I let 2" material soak? Overnight good enough?

[Scott Hackler]

2" to 2 1/2" would be fine for the roughout for most woods. From my experience Oak and Hackberry needs a little more because they always oval on me. As far as the Dna, softer open grain wood would be fine for an overnight soak, but I would soak a really thick hard wood bowl for a few days. I also triple newspaper wrap after the Dna bath and poke vent holes in the opening of the blank for the drying process.

[David E Keller]

I use the '10% of diameter' rule for determining wall thickness of roughouts... Never turned anything that big, so I can't be too specific about soaking times, etc.

[Steve Vaughan]

I'd agree with Scott, I think you'd be fine at the 2 or 21/2 and an overnight soak. I've seen others on here mention that they'd left stuff in for longer with no adverse affect and I've left stuff soaking for several days myself. I don't think too long is much of a concern. And the wood type will make quite a difference too with the oval-ing. I had some small roughed out bowls of gum and they oval-ed really bad...it was a really good thing I left them a bit heavy.

[Bernie Weishapl]

I use the DNA method on some pieces if I am in a hurry. I leave fruit wood 5 to 6 days. Big pieces thicker than 1" I still soak 5 to 6 days. I feel overnight is definitely is not enough soak time. If you are not in a hurry I coat the whole bowl with anchorseal, store in a cool dry place with not much air movement and on the floor.

[Nathan Hawkes]

I really don't have any experience with this, but it sure sounds like a recipe for disaster. Trying to dry out something quickly which is that thick is going to create some amazing stresses on the wood. I hope it works well for you. Please keep us informed!

[Reed Gray]

Check out this guy. I met him at a show in Seattle, and he turns big a lot. Seems like most of his were green turned to final thickness and allowed to warp. I really liked his stuff. Contact him, he might talk to you.

http://www.vkleibrant.com/

robo hippy

[Jim Burr]

Although mine aren't big, like Bernie I use a lot of fruit wood. I have no problem leaving it in DNA for 2 weeks to ensure all "water" is displaced. Since the alcohol is a muck lower specific gravity, it will displace/evaporate must faster so the multiple paper wrap is a great idea. So far, it's worked on apricot, peach, walnut, pistachio and grape...still working on almond:o

[dirk martin]

Trouble is, I am in a hurry for these to dry. I've got dozens and dozens to turn....if not hundreds. So, I'm searching for the fastest way to get these dry, and thus far the DNA method sounds like the quickest.

[Reed Gray]

If you are in a hurry, there are a couple of things you might do, but would require money. You could boil them. This ruptures the cell walls, and allows the entrained water (stuff on a molecular level) to get out more easily, and stabilizes, or at least releases a lot of tension in the wood.

If you have a large micro wave, it can be done that way.

You may want a solar kiln.

You may want a vacuum kiln.

You may want a light bulb convection kiln (most of the time done with an old freezer. A dehumidifier kiln is similar.

Other than the above, you have to wait, which actually gives you more time to turn. If you will have on going demand, then eventually you will get your stock rotation to the point where there is always some thing to turn green, some thing drying, and some thing ready to finish turn. The kilns will speed up the drying process, but you will have to experiment to find out what works. Of course, it can be a lot different for each different species of wood you are trying to dry. If you dry too fast, it cracks, if you dry it too slow, it molds.

The one advantage to green turning is that a 3/8 inch thick bowl will dry in my shop in about 2 weeks. Customers seem to like the 'organic' oval shapes.

robo hippy

[Scott Hackler]

Dirk, your in a catch 22. If you speed it up too much your going to get cracks and extreme warp. The DNA method, for me (in Kansas' climate), works better than any other method I have tried. I have done: roughed and in a paper bag, roughed and stuffed with shavings in a paper bag, left out on the floor, anchor sealed and wait for 6-8 months.

The Dna method, for me, drys a roughed out _____ in 2-6 weeks, most of the time variables are with the different wood varieties and the form. A hollow form takes longer for me to dry than a open bowl.

FYI



Trouble is, I am in a hurry for these to dry. I've got dozens and dozens to turn....if not hundreds. So, I'm searching for the fastest way to get these dry, and thus far the DNA method sounds like the quickest.

[Kim Ford]

Dirk;

I have done a good amount of research on this and would suggest you look into a vacuum kiln. Look on internet and you will find some very useful information. They are not cheap, to buy or build, but my research indicates that they will dry up to 2" wood very efficently in 3-4 days.

I bought a vacuum pump and am in the process of building a vacuum chamber that will take two bowls up to 24" in diameter, but am not there yet. In addition to the pump and the chamber you need to have a contact source of heat as well and a moisture seperator. Most commercial units use heat strips, the wood needs to be brought up to about 95 degrees F.

Commerical units are available but pricey. I know of a person in the flat stock hardwood business who has one and he says that they work very well and produce excellent results up to 8/4 stock.

Hope this helps.

Kim

[dirk martin]

Reed....why do you omit the option of DNA drying?
From my research, that seems to be the fastest, with least warpage, cracking, and other degradation.

Scott, I fully agree.

Kim, aren't vaccuum drying methods for flat stock, not bowls? I doubt a vacuum kiln will handle my blanks, which start out 10 - 15 inches thick...sometimes more.

[Kim Ford]

Kim, aren't vaccuum drying methods for flat stock, not bowls? I doubt a vacuum kiln will handle my blanks, which start out 10 - 15 inches thick...sometimes more.


Dirk; they go in the kiln after they are roughed out, so your thickness in 2" +/-. Maybe this will help.

http://www.svwoodturners.org/Newsletters/2006/10-2006.pdf

[Reed Gray]

I have used lumber from vacuum kilns, and it is super. 8/4 boards were dried in 7 to 9 days. Temps were up to 120 or so. Wood worked like air dried as in you rip a board on the table saw, and you get shavings, not dust. Same with a solar kiln.

robo hippy

[Barbara Gill]

I have used the denatured alcohol drying with several large (>20") bowls with great success. I used this method because the wood was prone to blue stain (Holly and Magnolia) and it was summer. I followed Dave Smith's directions to make the wall thickness less than the 10% used for air drying. My goal of no blue stain was accomplished and the deviation from round was small. There were no cracks. I don't remember the drying time as it was not important to me.

[Jamie Buxton]

If you're considering vacuum kilning turnings, there's turner named Joshua Salesin who wrote a short book about it. I've heard him talk about it, but haven't tried it. He's quite an advocate for it, and does make beautiful turnings.

http://joshuasalesin.com/

http://vacuumkilndrying.com/

[dirk martin]

yes but my understanding is that vaccume kilns put tremendous pressure on the wood...which is fine for lumber or slabs, but doesn't work for roughed bowls.

[dirk martin]

I have used lumber from vacuum kilns, and it is super. 8/4 boards were dried in 7 to 9 days. Temps were up to 120 or so. Wood worked like air dried as in you rip a board on the table saw, and you get shavings, not dust. Same with a solar kiln.

robo hippy


Reed, I'm drying bowls...not lumber. I'm well aware of the super benefits of vacuum drying for lumber, but my understanding is that they put lumber under tremendous pressue in these vacuum kilns, so I would imagine it would bust bowls. I thought vacuum kilns actually put a "blanket" of sorts on the lumber that really put pressure on the wood. Maybe you know otherwise?

[dirk martin]

I have used the denatured alcohol drying with several large (>20") bowls with great success. I used this method because the wood was prone to blue stain (Holly and Magnolia) and it was summer. I followed Dave Smith's directions to make the wall thickness less than the 10% used for air drying. My goal of no blue stain was accomplished and the deviation from round was small. There were no cracks. I don't remember the drying time as it was not important to me.


Barbara, I'm very interested in what you are writting.
Can you please elaborate on "the wall thickness less than 10%..." part of what you wrote?

[dirk martin]

Dirk; they go in the kiln after they are roughed out, so your thickness in 2" +/-. Maybe this will help.

http://www.svwoodturners.org/Newsletters/2006/10-2006.pdf


Wow...great info.
I've read a lot about vacuum drying of lumber, but I've never found an article on how to build a small vacuum kiln. thanks a ton for this info, Kim.

[Leo Van Der Loo]

Water does not exist under absolute vacuum, it boils off and becomes vapor.
That is the principle where a vacuum kiln works on, not pressure.

[dirk martin]

Makes sense.
Thanx, Leo.

[Nathan Hawkes]

I think you're going to be hard pressed to find a suitable strength tube and flange assembly large enough to hold a 26" diameter bowl, let alone several of them. You might be able to fashion something out of plexiglas, but you'll need thick stock for it; probably 3/4" or 1" thick. Remember a vacuum is 14.7psi, much more pressure than something designed for holding liquid. I've made quite a few aquarium filters & a couple aquariums over the years. I've got a stockpile of thick acrylic that I had intended to make a tank out of; it never happened. I'd thought that a vacuum tank might be a good use of it. The stuff is NOT cheap however.

[Dan Hintz]

I'm jumping into this one late, so I apologize if I'm missing something about the process.

If all you're trying to do is place a piece of wood under vacuum to boil off the water, why not use a vacuum bag like they use to wrap carbon fiber parts in before heading to the autoclave? The bags are relatively cheap (around $1 square foot), since you're not using them with epoxy they can be used time and time again, and they can be had in sizes nearly as big as a car (make any bowls that size?).

[Mike Davis NC]

If you read the original research on DNA drying you will see that bowls can be turned much thinner than 10% of diameter without splitting, cracking or shrinking irregularly.

I would turn one 20 inch bowl to 1/2 inch thick, soak it overnight or up to 24 hours at most, wrap the OUTSIDE in brown paper and tape along the rim so the inside is exposed.

Allow to dry until the weight stabilizes - usually about 8 - 10 days.

You may be surprised at how well your bowls turn out.

[dirk martin]

I'm kinda leaning towards what Mike is saying....
The DNA method is pretty simple, and not that expensive.
And, a week or two to get a finished result, is very good.

Now, the bowls I'm making, are not for final use.
I'm supplying these bowls to a group of others....thus they will be only roughed out. My audience needs them dry, however.

So, I'm leaning towards roughing them to 1" or 1.5", soaking them 24 or 48 hrs in DNA, then drying them in a week or two.

From what I'm reading, I may be able to achieve the same thing with a vacuume kiln with a dry time shorter than two weeks, but the hassle of building it I'm not too fond of. I do like the idea of having a small vacuum kiln, as I have an unending supply of stock to be dried (Anyone know of someone selling a small "hobby size" vacuume kiln kit?).

But, for now, it looks like DNA is the best choice for me.

[Ralph Lindberg]

Reed....why do you omit the option of DNA drying?
From my research, that seems to be the fastest, with least warpage, cracking, and other degradation.

....

Ask your self this question.

If DNA is so good, why isn't it used commercially?

A few years ago I had the chance to talk to a forest products guy, that actually knew about DNA drying experiments that had been done.

PS, there is a great piece from Texas A&M (?) on using DNA as a step in preserving wood some various sunken sources, like ship wrecks. Makes an interesting read

The issues for the industry is cost and unpredictable results. I can tell you that they found wildly unpredictable results, from the same specie of tree. They also found that the total cost for DNA was too high.

DNA is probably fine for the hobbiest or small production environment, but for large scale... Air Boil, Heat-Kiln, Vacuum-Kiln or Boil are probably better.

There have been some great home kilns done, using various boxes (old Refers, old dish-wahers) and a light bulb as a heat source

Personally, if I need it fast, with a low failure-rate, I boil (see Steve Russell's piece on boiling)

Boiling is actually rather easy, I just use an old turkey fryer, works, well and I have had zero failures with tough to dry woods (like Madrone)

PS there is a great article by a Texas U (A&M?) that talks about using DNA as a step in preserving sunken wood. Like the wood from a ship that sank. Good read and an interesting read

[Barbara Gill]

Barbara, I'm very interested in what you are writting.
Can you please elaborate on "the wall thickness less than 10%..." part of what you wrote?

Go back and check Dave Smith's instructions to get the best idea. I left the wall thickness at about 1 1/2" rather than 2". There was ample wood left to turn out the slight warp.
Dave Smith did a great deal of research. Over time many turners have given advice contrary to Dave's original instructions which is fine if they have researched and documented their results as well as Dave did.

[Barbara Gill]

If you read the original research on DNA drying you will see that bowls can be turned much thinner than 10% of diameter without splitting, cracking or shrinking irregularly.

I would turn one 20 inch bowl to 1/2 inch thick, soak it overnight or up to 24 hours at most, wrap the OUTSIDE in brown paper and tape along the rim so the inside is exposed.

Allow to dry until the weight stabilizes - usually about 8 - 10 days.

You may be surprised at how well your bowls turn out.

Mike, in my experience a 1/2" rough turned wall thickness would not have left enough wood to turn the bowl round and have enough wood left for a bowl of that size.

[Reed Gray]

Dirk,
I missed your post about me not mentioning the DNA soaking. I turn thin (1/4 to 3/8 inch thick), and let them dry and warp. The DNA soaking, in measured tests I have done, has no noticeable or measurable effect on this type of bowl. No difference in drying time, none in stability/warping. None in crack prevention. I say this after drying several hundred bowls in DNA, maybe a thousand or more air dried, and thousands that were soaked in LDD. I still use the soap soak because it makes a big difference in how the bowls sand out. The sanding is a LOT easier if I soap soak.

I don't think I have ever thick turned, dried, and then returned.

robo hippy

[dirk martin]

I can see that Reed, because of how thin you are turning them.

For my application, I will be leaving them 1 to 2 inches thick, and only roughing.

[dirk martin]

Very good points, Ralph.

If DNA is so great on 1" thick, rough bowls, then I would indeed think it would work great on 1" thick rough lumber...but nobody does lumber that way.

It takes about 2 weeks to get a bowl dry from start to finish, using DNA. It takes months for lumber.

It's probably also a volume thing. Soaking 4,000 BF of lumber in DNA would be quite a task.

So, since I don't have room for a kiln, and I'm only roughing these bowls to 1 or 1.5" inches thick, and need to dry them as quickly as possible, I think DNA might be best. Tho, a previous post mentioned boiling. .... I'm aware of the boiling technique, but am not sure why I decided to not go that route. so I'll look into that a bit more, too.

[dirk martin]

It looks like after soaking blanks in DNA, they'll be dry in 10 to 14 days (assume large 15" + diameter blanks) with walls 1 to 2" thick.

Can anyone tell me the speed to dry similar sized roughed bowls, after boiling 2 hours?

[Scott Hackler]

Dirk, what species of wood are we talking about here? I think 2" thick rough out using the Dna method is going to take longer than 14 days. From my personal experience, drying time ranges from 3-4 weeks for Maple, Box Elder, Elm, various fruitwoods and 4 weeks or so for Hackberry and 4-6 or more for fresh cut Black Walnut (takes forever).

I dont weigh my wrapped blanks but I smell them after 3-4 weeks for ANY trace of an alcohol smell. No smell = their ready to unwrap and re-turn.

[Reed Gray]

I really don't know if anyone has done a side by side comparison of the drying methods, where blanks are measured for drying times and warpage. It would make an interesting comparison test. One thing the DNA soaking did for my thin bowls was to make them harder to sand out. Almost like case hardening.

robo hippy

[dirk martin]

Primarily black walnut.
Some Red Maple.
Some Elm.