DNA drying question (Steve Schlumpf?)

[David DeCristoforo]

Most of what I have read on DNA drying has to do with bowls. The paper wrap is usually taped over the edge of the bowl so that the inside is uncovered. But my piece is a HF so there is only a small opening. I'm wondering if leaving the opening uncovered will provide enough air circulation for the piece to dry out. Anyone?

Thanx
DD

[David E Keller]

I usually wrap with newspaper and stuff it down in the hole... Then I wiggle my finger around in the hole to make sure there's an opening. It's worked for me. YMMV

[David DeCristoforo]

When you do that do you just use one layer of newsprint? I have a roll of brown package wrapping paper. Would that work? Is news print more porus? There's a print shop really close and they will let me have newsprint end rolls for free...

[Steve Schlumpf]

David - that's all I have been doing and it has worked for me. If the HF has a large enough opening, I will run the paper into the HF a little and tape in place. If the opening is small, I usually paper right over it and then come back and poke a hole through the paper at the opening.

The small opening will still allow air movement but I do believe the entire process may slow down a little because of the limited air movement. When I wrap mine after DNA, I usually do not go back to finish turn for a couple of months or longer, so I have no idea how long it actually took to dry out enough to finish turn.

Hope that helps some.

On the paper topic - I use brown paper bag. It is heavy enough that one layer works fine. The newspaper wrap seems to work well for a lot of folks - I just didn't want to mess with multiple sheets of paper and getting the ink smeared all over everything.

[Ken Whitney]

I've been doing the DNA thing for a few months with pretty mixed results on pear, mulberry, etc. I have been soaking in DNA for several hours (occasionally overnight) and I wrap with newspaper and tape, following Dave Smith's directions. I have had lots of catastrophic failures, and quite a few with end-grain checks.

I live in California and the temperatures are high in summer and the humidity is very low. I suspect the paper barrier just doesn't slow moisture loss enough to prevent cracks.

I just started experimenting with stretch wrap (the stuff used to bind palette loads, etc.) as the only wrapping medium. Very preliminary results seem to indicate that this has, under the conditions in my shop, stopped the checking and cracking problem.

It does slow down moisture/alcohol loss from the roughed out blanks quite a bit, almost to the point of being too slow. I'm going to try and determine what percent weight loss is necessary to prevent checking, before removing the wrap.

Another point that seems relevant is that since wood on the heartwood side shrinks less than wood on the sapwood side, it may make sense to expose the heartwood side to the air, regardless of whether that is the top of the bowl (i.e. the open end) or not. More experiments are in order.

[Scott Hackler]

Ken,

The humidity here in Kansas is at about 99.99998%, most of the time; but I have my stored roughouts in my air conditioned where the humidity is a lot better and I dont have the same results you've experienced.

One thing I (and most using Dna) are doing different are the soak times. I soak everything a minimum of 24 hours and any fruit type wood gets 3-4 days. I then triple wrap in newspaper, really really tight and tape it shut. the opening of the bowl or HF or whatever has a hole cut into the newspaper for breathing and I store it all on a shelf, hole down for 1 month to 2 months or so depending what variety I cut up. I can honestly say that I have almost a 99% positive success rate, with no checking or cracking. I am 100% sold on this method and it cut my finish time to 1/4 of the anchor seal method.

Keep trying and have patience.

[Scott Hackler]

I forgot to add that I smell the opening and if I can smell the Dna I know its close to being done and the newspaper is usually loosely fitting at this point.

[Harvey Ghesser]

Here's my .02 worth...I soak in DNA a minimum of 24 hours then after about a half hour or so drying in open air, I place the rough turned bowl in a brown paper bag sealed with masking tape and place it on the floor or under my workbench for about two months.

99.9999% of my roughouts survive without cracks. And I do a lot of bowls. I won't change a thing. Works for me...

[Rich Aldrich]

I am not sure how my experience will help you with hollow forms. I have only made bowls, but have found the drying time for a bowl is less than one month. I turned one after 14 days and it turned out ok.

I soak the bowl for 24 hours and air dry about 20 to 30 minutes and then wrap with grocery bag paper. Normally, I end up with a place to breath over the inside of the bowl - that is normally where the seam ends up and where I tape it.

I havent lost a bowl to cracks from DNA drying. I have lost one due to cracks in final turning - a knot was too close to the rim. Another ended up shorter than the original intended height.

[Ken Whitney]

David and I live a few miles apart. The relative humidity in the Central Valley of California can get into the 30% range and lower. Not to mention the high summer temperatures (often in excess of 100). I envy you guys in Michigan, Virginia, etc. with high relative humidity, at least from the aspect of bowl drying.:)

My experience with putting a paper barrier over rough-turned bowls (which is, in essence, a layer of "wood"), does not sufficiently slow the loss of water to prevent cracking and/or checking. I have had success with DNA (and other methods), but I do get what I consider to be an abnormally large number of substantial cracks, compared to the experiences I've read about here.

I think stretch wrap or shrink wrap as a barrier may be helpful in DNA drying in low RH areas.

[David DeCristoforo]

So from what I have gleaned here and elsewhere, my plan is to let the piece soak until tomorrow afternoon. Then I'll air dry it for a half hour and wrap it in newsprint, leaving the opening... well... open. Then I'll loosely wrap that in "Saran" wrap being careful not to cover the opening. Then we'll see what happens. I have a moisture meter and I have found that somewhere between 12 - 15% is "perfect" for turning. Not as dry as I liked my wood when I was doing "flatwork" but it seems to be plenty stable enough at that level and much nicer to turn. So when my piece gets down to that range, I'll open the "package" and see what I've got.

Thanx to all for the input...

[Richard Golde]

There is something that hasn't been mentioned yet to slow down the drying in low moisture environments. Put shavings in the inside or the outside of the bowl or hollow form and then wrap the piece in brown paper. That will slow up the drying and help stabilize the drying.
Richard Golde

[Rob Cunningham]

I have been soaking my HF's in DNA for 3-4 days. Pull them out and let them dry for @ 1/2 hour. Then wrap with 2 layers of newspaper and cut the paper around the opening. I store them on a wire rack, opening down, that's about 18" off the floor. So far I haven't had any failures.

[Leo Van Der Loo]

So from what I have gleaned here and elsewhere, my plan is to let the piece soak until tomorrow afternoon. Then I'll air dry it for a half hour and wrap it in newsprint, leaving the opening... well... open. Then I'll loosely wrap that in "Saran" wrap being careful not to cover the opening. Then we'll see what happens. I have a moisture meter and I have found that somewhere between 12 - 15% is "perfect" for turning. Not as dry as I liked my wood when I was doing "flatwork" but it seems to be plenty stable enough at that level and much nicer to turn. So when my piece gets down to that range, I'll open the "package" and see what I've got.

Thanx to all for the input...

Up here I take a little bit of non denatured alcohol, Cheers, then take my roughouts and put them in a brown paper bag, close it and place it at a cool place with no draft, and that has worked for me for many years with very good results.

I read all the stories about drying it quickly and using alcohol for that, how does that fit in with slowing the drying down at the same time ????
I must be very dull but fast and slow just doesn't fit in the same box up here, good luck with your drying, I do know what works well without all the mumbojumbo :eek:

[Rich Aldrich]

David and I live a few miles apart. The relative humidity in the Central Valley of California can get into the 30% range and lower. Not to mention the high summer temperatures (often in excess of 100). I envy you guys in Michigan, Virginia, etc. with high relative humidity, at least from the aspect of bowl drying.:)

My experience with putting a paper barrier over rough-turned bowls (which is, in essence, a layer of "wood"), does not sufficiently slow the loss of water to prevent cracking and/or checking. I have had success with DNA (and other methods), but I do get what I consider to be an abnormally large number of substantial cracks, compared to the experiences I've read about here.

I think stretch wrap or shrink wrap as a barrier may be helpful in DNA drying in low RH areas.

Actually, in the winter, the realitve humidity in the shop is probably less than 30%. When it is cold, less than 20 F, sometimes as low as -25F, the air in the shop gets real dry from having to keep the place heated.

I get nose bleeds just from breathing.

[David DeCristoforo]

"I read...about drying it quickly...how does that fit in with slowing the drying down at the same time ????"

Maybe it dries faster but not too much faster? I might not be thinking about this if I had a big stash of wood that was "dry and ready to turn". But being pretty much of a newcomer, and not being so young that I can indulge the luxury of having wood laying around drying for eight or ten years or more has gotten me interested in anything that might hurry things up a bit.

[Ken Whitney]

Actually, in the winter, the realitve humidity in the shop is probably less than 30%. When it is cold, less than 20 F, sometimes as low as -25F, the air in the shop gets real dry from having to keep the place heated.

Still great conditions for bowl drying. Moisture loss is proportional to temperature and inversely proportional to relative humidity.

So in summer the high temp is offset by high RH, and in winter the low RH is offset by the (very) low temperature.

But if it is that cold, the water in the wood freezes. Frozen wood + low RH = freeze drying!

[Harvey Schneider]

DNA dehydrates the wood. It removes most of the water by dilution and leaves alcohol in its place. The alcohol evaporates quickly but the residual water still needs to be removed.
The issue is not slow vs fast. The issue is to maintain uniform moisture content in the wood so that it shrinks evenly. The expectation is that the overall process is faster than a sealed paper bag and that the survival rate of the roughed blanks is higher.
I may be a product of the "instant generation" but I don't have the time or the patience to wait a half year between roughing and finishing a bowl.

[Leo Van Der Loo]

If this is true, the alcohol takes the place of the water in the wood, where does the water go to ??, and then everyone seems to keep on using the same batch of what is now surely all water after a few bowls have all the water taken out of the wood and replaced by alcohol.
There have been a couple of trials of side by side drying bowls from the same wood and same size etc, and the outcome was "no difference using alcohol or not"
I'll give you one more question, if alcohol moves through the wood, why are wine and spirit distillers using wooden casks, and neither the alcohol or water leaves the cask over not days or weeks, but not in years.
Big saw mills use expensive heat to dry their wood in kilns, why would they not use cheap alcohol that they even could recapture if needed ??

Oh I turned a bowl from the Siberian Elm I cut down about 10 days ago, it is dry now, just wasn't very thick but it doesn't take regular bowls that long to dry, it is the splitting that's the biggest problem when we try to dry bowls faster and not evenly, it is the wrapping around the bowls that makes the wood dry more evenly, that's what I use also, without the alcohol/water or whatever your vat now contains.

[Leo Van Der Loo]

A kiln might be the better thing to use for faster drying wood, rather than soap soup, boiling vats or alcohol buckets, that's of course just my opinion, have fun and take care ;-))

[Bill Boehme]

There were several patents issued in the first half of the 1900's for stabilizing wood to reduce wind and warping by soaking in ethyl alcohol. According to the claims in these various patents, the soaking process slightly softened the lignin in the wood which relieved a significant amount of the built in reaction stresses (in other words, the stress from supporting non uniform loads on opposing sides of the diameter of the log) which is a primary cause of movement in wood as it dries. The goal in these patents was to improve the yield of lumber back in the days when bad boards were culled.

It turned out that none of these methods were commercially viable except for specialty products because of the increased cost. The problem of improving yield has been successfully addressed these days by not culling anything that even remotely resembles a board.

None of the patent claims that I saw mentions faster drying.

[Leo Van Der Loo]

Yes claims.
claims that the alcohol replaces the water.
claims that the wood doesn't shrink or warp.
claims that the wood dries faster.
claims claims claims

[Scott Hackler]

From my experience:

I used to coat the outside of a roughed out bowl with anchorseal and sit it on the shelf. It would take 6 to 8 months or more for the wood to dry (stop loosing weight). Great success but really slow for my taste. I researched the Dna method and thought I would try it. From my understanding; the Dna exchanges place with the majority of the water in the wood and does something to the cell walls of the blank that allows for a very consistant evaporation of the Dna and allows for a fast dried rough out without warping or cracking.

Eventually a non refreshed bucket of Dna wouldnt work well because of the water content mixed into the Dna. Adding a gallon here and there eliminates that problem and keeps the ratio at an usable level.

Again, in my experience, this method of an overnight soak in Dna and being wrapped up in paper is at 99.9% sucessfull. Most of my blanks are fully dried and ready for final turning / finshing, within 1 month. I see no adverse effects of using a technique that has been proven to work. The only downside would be the combustable nature of the Dna and the possibility of igniting it if your not using common sense.

Air drying is crap and I lost almost everything. Same with just wrapping the blanks and waiting. Stuffing the blanks didnt work for me either. They never fully dried out the most have mold forming on teh inside where the shavings where.

As far as the saw mills using Dna vs. a kiln. A giant kiln is way more cost effective that an olympic swimming pool full of Dna and the labor of fishing them out and wrapping the boards. A kiln might be ideal, but even that isnt 100%, as noted the last time I had to spent an hour fishing though the entire pallet of 2x4's looking for 10 straight boards!

I guess it all boils down to what works for you. Every climate are is probally going to see different work. If covering it in dish soap is the trick for you... go for it, boiling or microwave or anchorseal... do it. The Dna technique works absolutely great for me and many others. I really love having the option of going from log to dried blank in 1 month.

[Leo Van Der Loo]

Well maybe next time you should do exactly what you do now with a couple of similar bowls except have one not soaked in the DNA, then dry next to each other and see if there's a difference in drying, you might be surprised in the outcome, but like you say do what works for you, I certainly have no objection to that, I just find it unnecessary, wasteful, and have never found these procedures to work as is claimed, have fun and take care :D

[Ken Whitney]

Back in my college days I used to do electron microscopy. There is a process for preparing soft biological specimens for scanning electron microscopy called critical-point drying. It worked something like this:

1) Fix the biological material in a chemical fixative (alcohol, formalin, etc.).

2) Run the specimen through an ethanol gradient (i.e., 20% ethanol, 40% ethanol, etc., right up to 100% ethanol). If I recall correctly after 100% ethanol you put the specimen in to acetone, but I'm not sure about that step. The point is that the water in the specimen would slowly be exchanged with ethanol until all of the water was removed and replaced with ethanol.

3) Now the "critical" part. The specimen was placed in a pressure vessel and the vessel was flooded with liquid carbon dioxide to flush out the ethanol and replace it with liquid CO2. Then the pressure vessel was heated, and the CO2 reached the "critical point" where the liquid phase instantly converted to gas. The gas was then bled off and the nice, plump specimen was retrieved.

Whew!

I think that DNA bowl drying mimics this process to a certain degree. Some of the water in the rough out is replaced with alcohol. Alcohol is less "polar" than water, it evaporates easier (lower boiling point, etc.), and it induces less stress on the wood than water.

At some point during the soak the alcohol content of the wood will match the alcohol content of the DNA solution. Obviously the higher the alcohol concentration in the solution the higher the alcohol concentration will be in the wood.

There is, of course, a tremendous variation in wood species response to drying, and I think that local conditions greatly impact the outcome of any drying method. In one of Mike Mahoney's videos, he mentions that he coats the whole bowl with Anchorseal, due to the low humidity in Utah. Scott's point about local variation is right on the mark.

[Kim Ford]

David, there are many different ways to dry bowl blanks and reading through this thread has been interesting and very informative. I have tried many of them and have settled on the following for most cross grain woods because it produces the highest percentage of useable blanks given the woods and the shapes I turn.

1) Make sure the roughed out blank is consistent. Usually walls about 1" or 10% of the diameter.
2) In a brown grocery bag they go with a handfull of shavings from the rough out process; fold over the opening and staple shut. I write the date, wood type and size on the outside of the bag with a magic marker.
3) They go in the back room out of the sunlight with little ventilation for as little as 3 weeks or I still have some back there from a couple of years ago it just depends on the wood, the shape and the desire I have to finsh the bowl.

When it feels like Christmas, I open them up, CA any cracks, let then stablize for a day or two, then put them back on the lathe and bring them to round again. They then go in my to do pile which is just open shelves.

It's just my thing, but as you can tell I am not a "green wood" turn and finish guy. There are some great pieces out there done that way but mine always seemed to look good the day I take pictures, and then when I see them a year latter they just didn't have the appeal they had when the final distorting is done. So I have settled on this process and it works for me. It does take some time get into production and if you get a special piece of wood you have to wait until it is dry to finsh it out, but in my opinion it is worth it.

[Scott Hackler]

Well maybe next time you should do exactly what you do now with a couple of similar bowls except have one not soaked in the DNA, then dry next to each other and see if there's a difference in drying, you might be surprised in the outcome, but like you say do what works for you, I certainly have no objection to that, I just find it unnecessary, wasteful, and have never found these procedures to work as is claimed, have fun and take care :D

Leo, I have done just that and had some success and some failures. I do believe that the Dna soaked blanks dried faster than the unsoaked ones and from the cracks and warped results I find the Dna method actually have a noticable benefit for ME. Now wether that has something to do with the unbearable humidity in Kansas, I dont know. What I do know is that I absolutely hate loosing a beautiful piece of wood from crackling and warping and since I started with Dna..... I getvery little of either. Almost to the point of NONE. Im as tight as they come and if I could achieve the same results without the Dna expense, but still in the same time frame I would be trying it too.

[Bill Boehme]

Better than alcohol, kiln drying, critical point drying, microwaving, or waiting years for wood to dry is to be fortunate enough to live in Texas where mesquite literally grows on trees. Green mesquite can be turned start to finish in one session with almost no distortion. For purists who must air dry before final turning, one week is normally sufficient during the summertime in Texas (which is a close approximation of kiln drying). Ya'll better hurry up and get here 'fore all the folks who use it for cooking barbecue and fire wood get it all.