I need some advice on drying bowls.....

[Ken Fitzgerald]

I have had virtually no success getting green roughed out bowls to dry without cracks. Most of the wood I've been using has been fruitwood and I understand a fruitwood bowl without cracks is a gift from a higher power. But now I'm having the same trouble with maple. Is this normal for maple or am I doing something wrong.

I just posted a bowl I finished from maple burl. It started out with walls 3/4" thick and it was about 7 1/2" diameter roughed out.

I just pulled another one from the same piece. It's about 6" in diameter and it's got a tremendous crack in it but the walls were only 1/2" thick.

Should I make my walls thicker....thinner.....Any suggestions besides go to segmented turning would be greatly appreciated!

Thanks

[Mike Vickery]

Ken,
Others may know than me but the wall thickness sounds fine to me. Maybe you could give some info on your drying process?

[Ken Fitzgerald]

Mike....I've been rough turning the green blanks to a wall and floor thickness of 3/4" and then soaking them in DNA for 2-3 days. Then wrapping then in 2 layers of newspaper. I tear a little hole, maybe 1" in diameter in the center of the bowl near the inside bottom and then let them dry for 3 weeks or so.

[Stu Ablett in Tokyo Japan]

Hey Ken, sometimes it just happens, nothing you can do.

one thing I notice that is different that you do than I do, is the size of the hole in the top of the paper, I cut the hole as big as the opening in the bowl, dunno of that will help, but I've only had one bowl go crack on me, but I'm not doing a bunch of fruitwood.

Good luck!

[Dominic Greco]

Ken,
It might not be the drying process at all. It might be the way that the blanks are cut from the log.

When you cut up a log into blanks, are you making sure that the chainsaw cut is oriented to yield a blank with even grain distribution? In other words, the grain of the wood should not be tight on one side of the blank, and widely spaced on the other. Uneven grain distribution will cause the blank to dry unevenly, thus causing a lot of movement and sometimes cracks. When you said that the bowl really distorted when it dried, that gave me the idea that the grain density was not even across the bowl.

It took me a while to get the hang of this. But once I did, I noticed that my bowls would stay rounder when they dried, and that they would not go oval once I final turned them.

If you check back about a month or so ago, someone else had a similar problem. I answered the same way, but Bob Hamilton posted a picture that showed what I meant far better than my explanation. Here is a link to that thread

Ugh, turning out of round bowls (http://www.sawmillcreek.org/showthread.php?t=53296)

Something else just caught my eye. You say you DNA soak for a 2-3 days? When Dave Smith first started experimenting with DNA soaking, he asked me to evaluate the process. If I understand his directions correctly, you need to only soak the roughed out bowl overnight. Not that what you're doing is wrong or will harm the blank. It's just that it's not entirely necessary.

[Mark Pruitt]

Ken, I would try soaking for less time, like 24 hours. Then let it sit for a month. Just a suggestion.

[Christopher K. Hartley]

Ken, permit me to suggest something. Two layers of newspaper is, in my experience, not enough thickness to adequately slow the drying process. It does not offer the same restriction qualities as a brown paper bag. I use a minimum of six sheets and find minimal problems with cracking and warping. Also, depending on the wood you may need to vary the drying time. I use two weeks as a standard but on some woods with a lot of movement I will go as high as four weeks. I will be experimenting with the soap method as soon as "Beauty" comes in and I will keep you posted on the results. Consistent wall thickness throughout the bowl is critical to limit cracks so be sure it is the same thickness throughout. Generally, twenty-four hours in DNA is sufficient soak time unless the DNA has started to weaken.:)

[roy knapp]

Ken you may want to try this as it has work for me. I dont recall where i found out about this.
I have taken the green wood and turned it to the finished size and then put in in the FREZZER for 10 DAYS and then remove it and let it sit at room temp. for 3 to 4 days befor doing the finishing.
The bowl will go out of round but will not have any cracks or splits.
One other method i have been doing is the Microwave drying, again turn the bowl/platter to finish size (thin walls and base) and but in the microwave at minute interverals at high power. dont exceed a total of 10 minutes.
remove the bowl between 2 minute interverals and dry it off then continue as needed.:) :) :)

[George Tokarev]

No secret to getting the water out of wood. You just let the atmosphere dilute it to equalization. The process of drying is wonderfully described in chapter three of the Wood Handbook available free at. http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm

The things you want to concentrate on are the shape of the piece, the orientation of the annual rings, and the rate of loss to the atmosphere. What starts cracks is a dry, contracting surface over a damp, expanded interior. Since wood loses water through the vessels designed for its transport ten to fifteen times faster than through face grain, we often retard the loss by wrapping, coating, or otherwise containing within a larger, more humid environment to allow the interior to catch up. The tables in chapter three show that wood at 100% relative humidity contains approximately 30% moisture by weight. The fibers are saturated at that point, binding about as much water as cellulose is capable of. How fast you get to 30% is of no consequence. You can spin a lot of water out, blow it out with compressed air, even briefly expose to warm and dry air until the surface shows no color.

When you go thin, things dry faster. When you go real thin, say 1/4 inch or so with most domestics, the distance water has to travel is so short you almost can't make it crack. The other advantage to thin is that with a circular piece, thinner sections can't grab on to as much wood and contract the entire without deforming into thin air. Direction and dimension of contraction for common woods is listed in the chapter referenced.

You say "fruitwoods," which is something as descriptive as "spindle" gouge. Do you mean wood from orchard trees which are pruned for picking, a process which induces stress in the wood? I turn a lot of cherry, but it's grown in a competitive environment, with only natural self-pruning, and is as stable as any other wood. Open-grown trees of spreading habit have a lot of compression wood, while forest-grown specimens of the same species shed stressing branches quickly in the rush for light.

No formulas, no magic potions, just good sense. Keep your eye on the grain to spot trouble areas, keep your drop from 30 to 10 % slow enough to allow capillary draw and diffusion to keep the surface partially expanded. From my experience, 75% RH is enough to keep most domestics safe until equilibrium is reached. That's about 15% moisture content. About 3/4 of all the contraction is done by then, assuming you're going to ~10, and the piece can be put almost anywhere to finish curing.

How thick you start depends on what you want to have left to work with after curing. I like to leave at around an inch, knowing that, for instance cherry will lose 1/4 to 3/8" in total crossgrain contraction. Allows for some modification of shape or detail even in a thick walled style. If I was trying to dry faster, I could cut thinner. On stuff like birch or hard maple, I expect up to 1/2" loss. Works out fine, and they take a couple months to EMC, which is OK with me.

[William Bachtel]

Anchorseal the whole thing, if it is cracking it is drying to fast. I put mine in a fruit cellar for a month, where the humidity if 55%, no wind, no sun, and no high heat, no rain, it has to be constant. After a month I move them into the shop. I put one on the front porch (covered roof) and it cracked a little, back to the fruit cellar for me. Time of year that the tree is cut is a big factor. Try to cut in the dead of winter, when the sap is down in the ground, and the tree has little water content in the sapwood.

[Dave Wimmer]

I have had near 100% sucess with DNA soak for 24 hours, wrapping with grocery store bag paper secured around the rim with masking tape. The inside should be totally open cutting away everything all around the inside of the rim and allowed to dry upside down with plenty of air circulation underneath. A wire rack or shelf is great for this pupose I use a digital postage scale (about $25 on ebay) to tell when it stops losing weight. This has worked very well for me.
I have tried the dishwashing soap method also. Had no problems with cracking, but experiance more wood movement when drying.

[Bernie Weishapl]

Ken you have gotten a lot of good advice. Dominic hit the nail on the head. I have found if I cut a log in half with part of the blank having tight grain expanding into wide grain some of my bowls will crack on me every time. Also I soak for 24 hrs. and wrap in a brown paper bag. I have found newspaper does not work well for me unless I use as Mark does 6 to 8 layers. When wrapped in brown bag, masking tape around the rim to secure it I then cut out the middle clear to the rim but leaving the rim covered. I put it on a cooking rack used for cooling food bought at Wal-Mart. I put it upside down in a room where it is fairly dark, humidity is fairly stable, not to much air movement and let it sit for 3 or so weeks. Only had one crack on me in the last 6 or so months.

[Mark Cothren]

Two layers of newspaper is all I have ever used when drying bowls, platters and hollow forms. On bowls I cut a hole about half the size of the rim. I've done this with bowls 19" in diameter that were roughed about 1-1/2" thick down to bowls 6" in diameter roughed about 1/2" thick.

I also wrap roughed-out hollow forms with two sheets of newspaper and then just punch out the paper in the opening.

I think the issues you are having is not with the DNA and/or newspaper, but as has been mentioned - with the wood you are using and how it is cut.

I don't know how many turnings I have roughed, soaked, wrapped in two sheets and then dried for 2-4 weeks... but I can probably count on one hand - for sure on two hands - the number that I have lost due to cracks/warping.

That is just my own experiences and YMMV...

[Neal Addy]

Ken, have you tried the boiling method? It's worked well for me several times, although I haven't tried it on fruitwoods.

I just boiled a piece of Cocobola last night and don't expect any cracking. I figure on turning it within two to three weeks.

[Ken Fitzgerald]

Neal........I haven't tried the boiling method yet but I'm at the point where I"ll try anthing.....

I've even considered rolling some chicken bones on the floor under my lathe combined with some chants or maybe some cursing.....:eek: :rolleyes: :D

[Mark Cothren]

I've even considered rolling some chicken bones on the floor under my lathe combined with some chants or maybe some cursing.....:eek: :rolleyes: :D


You've been talking to Burns again, haven't you?

[Perry Higgins]

Ken,
I've been working with Pear wood (orchard trees removed from production) the last few weeks and I have yet to get the DNA process to work on this wood. In contrast, the dish soap process has worked without fail and the blanks are coming out of the same log. I'm no expert and not nearly as well versed as the other contributors, but for me out here in the dry west, DNA does not work on fruit wood and dish soap does. I'd suggest you give it a try.

[Bob Hallowell]

Ken,
I think I Know your problem,

here's what I found works-

walk around the lathe clockwise with your right hand touching it- stop scratch your head then walk around counter clockwise 2 with your left hand touching the lathe.

Let me know if it worked for you:D

Bob

[Ken Fitzgerald]

Bob.....I don't need any help causing my vertigo attacks to occur......I need help preventing or eliminating them!....PS....this didn't work well for me using a baseball bat instead of a lathe either!:D

[Mike Vickery]

Ken great advice you got especially about the grain orientation. Please keep in mind when it comes to news paper you climate has a lot to do with it. 2 sheets of news paper may work fine for someone in a more humid climate, but will not cut it for me in the desert. I believe you are in a pretty dry climate. One guy I watched and the woodworking channels has a simple and brilliant statement that works in all environments. If your bowl is cracking it is drying to fast, if it is molding it is drying to slow. You will have to play with what works for you to slow down drying. You can spray the outside with deft, wrap in more newspaper, put news paper in a brown grocery bag for a while, use anchor seal or many other methods to slow the drying down even more.
P.S. If you DNA is old you may want to consider replaceing, when mine gets old it picks up a lot more water and seems to decrease the the benefits quite a bit.

[Reed Gray]

All of the drying methods are centered around one concept, and that is to control the rate of drying. Too fast and it will crack. I generally turn to final thickness (1/4 to 1/2 inch) then LDD soak, then dry. I like the warped shapes. To dry, I start with them on the floor for several days, then move them up to a rack for final drying. They reach equilibrium in 1 to 2 weeks, depending on when they are harvested, and the time of year. My shop relative humidity is around 55 to 60%. Any knot, crotch, or other reaction wood, or uneven thickness will result in uneven stresses and increase the chance of cracking. Bagging, newspapers, burying in dry shavings/chips, anchorseal, or keeping in a humid area are all ways to slow down the drying process. With the soaking (LDD and DNA) I haven't noticed any difference in drying time, movement, or cracking rate. This could be due to my turning thinner, and maybe if I left them thick for returning, it may make a difference. Another experiment for me to try some time. The LDD method does make the bowls a lot easier to sand out when dry.
robo hippy

[Mark Cothren]

Please keep in mind when it comes to news paper you climate has a lot to do with it. 2 sheets of news paper may work fine for someone in a more humid climate, but will not cut it for me in the desert.

Good point, Mike.

[Ken Fitzgerald]

Guys......So far I've been just following what others have posted here in the past..........But all these post have got me to thinking.

Lewiston is dry.....almost as dry as the deserts in California, Utah, Arizona, etc. Our average total moisture is only 12" ....2 inches less we'd be a desert. My shop is heated and is currently set at 64 F...it's not too hot but our humidity is extremely low....Now we have some humid days but 30-40% is probably normal and often less than that....

I'm going to rough some out this weekend and try more news paper...try some brown paper bags.....and I think I'll try some boiling and maybe some dish soap. It's not like any of them will hurt my success rate. I know these methods work but so far, DNA hasn't produced a single success for me. My alcohol is relatively new. I WILL FIND A METHOD FOR SUCCESS!

Just in case, however, I will start saving some chicken bones!:D

[George Tokarev]

There you go. Invest ten bucks in a good hygrometer and find out what's really happening. Get a nice big appliance box or something similar to rack your roughs in, and monitor humidity.

Don't make the bottom of a cross-grain piece too broad and the sides too steep, or you won't get the benefit of radial shrinkage to counter the tangential. The outside of the bowl tries to pull fibers apart, the interior compresses them, so if you go the paper or anchorseal route, you need worry only about the outside. Any incipient crack inside will close automatically, and you might as well not slow drying too much.

[Jim King]

Boil those blanks.

http://www.exoticwoodworld.com/index.php?c=static&sc=boiling1

http://www.exoticwoodworld.com/index.php?c=static&sc=boiling2

[Keith Burns]

Ken, I really think the chicken bones are your best bet !!http://joetonich.forumup.us/images/smiles/oregonian_scram.gif (javascript:emoticon('[lv]'))

[Bernie Weishapl]

Bob.....I don't need any help causing my vertigo attacks to occur......I need help preventing or eliminating them!....PS....this didn't work well for me using a baseball bat instead of a lathe either!:D

Oh Ken in order to get rid of the vertigo attacks you do what Bob says but the other hand is tugging your ear. Works every time.:eek::rolleyes::cool:;)

[George Franklis]

Ken, I really think the chicken bones are your best bet !!http://joetonich.forumup.us/images/smiles/oregonian_scram.gif (http://javascript%3Cb%3E%3C/b%3E:emoticon%28%27%5Blv%5D%27%29)
I prefer turkey bones - dark meat only.

[Bob Jensen]

What works for me on a bowl that size is turning wall thickness to about 5/8" thick and making SURE the bottom is also sized about the same. I then soak in alcohol for 24 hours or thereabouts and then let it sit out for an hour to air dry and then i put it in a tyvek bag. Tyvek is the house wrap product you see everywhere, it lets moisture out but not in. I can say honestly that my sucess rate is probably 98% doing it this way. I do not use this on every bowl or vessel i make but i do use it for colorful, troublesome woods, highly figured wood, or wood that i buy. Fruit woods are certainly the worst, and have been my only failures, pear, and apple. Once i purposely left the pith in a large cherry bowl, it was at least 2" down from the top of bowl and to this day the pith is still there and not a crack anywhere around it. I really believe the biggest mistake is leaving to much wood in the bottom of roughout it tends to dry unevenly and has little option but to crack.

bob

[Curt Fuller]

Ken, I really think the chicken bones are your best bet !!http://joetonich.forumup.us/images/smiles/oregonian_scram.gif (http://javascript<b></b>:emoticon('[lv]'))

Not just any old chicken bones will work though. They should be KFC chicken bones. And what makes that work even better is using the old buckets from KFC for the drying. They have just the right sized holes in the lid for ventilation.

More seriously though, I'm not far from you in terms of climate and humdity and I have all kinds of problems keeping my wood from cracking also. I remember the posts about you getting the big maple tree and it was at the time of year when the sap is starting to really move up into the tree. I've had my best luck cutting trees in late fall/early winter after the leaves are off. And I think you want to slow or even out the drying process some in our low humidity. I use the rough turn and dna process too, but not until after the blank has been allowed to dry out somewhat (6-8 months) sealed in anchorseal. One thing I've found is that if there's enough water in a blank that it flings it on you as you're roughing out a bowl, then it's going to be hard to keep it from cracking and will take some extra care to do it. If the blank is dryed out some first I have much better luck.

[George Tokarev]

I really believe the biggest mistake is leaving to much wood in the bottom of roughout it tends to dry unevenly and has little option but to crack.

bob

Hmmmm. I don't agree. The thickness of the bottom has little bearing on the survival of the blank. My blanks have bottoms thicker than the height sometimes.

[Bob Jensen]

George,

Are those using the alcohol method of drying? I kept close records on the 1st dozen or so i tried the DNA on and found that in my climate they were as dry as they would get after 8-10 days in my tyvek bag. I helped several club member that were having problems with DNA drying and found that they all left the bottoms very thick and when they tried my approach they also have had great sucess.....i do believe that your climate and shop plays a huge role in this.

bob

[Ken Fitzgerald]

Bob....Just for the record, I used calipers to make sure the bottom and sidewall thickness were nearly identical before they were DNAd.

[George Tokarev]

No, Bob, my brief work with alcohol only confirmed that water evaporates at the same rate whether it's 5% alcohol by volume or not. In short, my Physical Chemistry text is correct, and Raoult's law applies.

If you look at the Wood Handbook available at http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm or R. Bruce Hoadley's Understanding Wood you'll find an excellent set of illustrations and information on how wood dries, and which directions you can expect it to shrink. All you need in your planning. After all, the determining factor in dry speed is how close any part of your turning is to open air through end grain, and the shape of the turning.

[Curt Fuller]

I wonder if the DNA has some kind of affect on how the water in the wood cells is able to get out, like if it breaks down something that allows the water to escape. I don't dispute George's scientific knowlege about water and alcohol but at the same time I know I've had better results soaking in DNA than not soaking in DNA and I don't believe in magic. There's something happening that increases the odds of a crack free bowl. Mine will usually warp about the same but they do it with much less cracking.

[Bob Jensen]

I wish i knew all the reasons why it works for me, is the tyvek bag the secret? Is it the climate? i live in Mn. But i went from approx. 30% failure rate to almost perfect. My shop is climate controlled pretty much but it was before i started the dna drying. All i know is that when i have a blank i don't want to lose whether its an exotic i bought or some highly figured local woods i dna those and have wonderful results.

Someone asked about the tyvek bag, it is a piece of tyvek that is about 18" x 36" i simply folded in half, taped 2 edges closed and have one end open to put blank in and then roll it up leaving no openings.

[George Tokarev]

It works because it doesn't make a difference whether you soak it or not. Tyvek is an interesting choice of materials. Don't know the standard for the material, but I imagine it's a bit more consistent than say wrapping in newsprint. Can you sterilize and reuse? Bags and paper regulate well because they're wood, and help maintain a buffered 30% equivalent. They do develop mildew if you're not careful, and it'll affect the next one you bag that much sooner if you reuse the bag.

I have a basement which offers quiet high humidity air for the second-stage drying, though I did bust a cherry bowl wide open when I left it underneath the heating duct overnight, where it received a few hours of dry warm air directly on it. Lit a fire for the first time that season without thinking. That was a couple years ago, and the next hundred or two did fine, so it isn't the alcohol.

[Bob Jensen]

Well now i'm curious, is it simply my tyvek bag? I am not so sure, but I will do a couple test pieces and find out for sure. For those not familiar with tykek it is a product widely used around here to wrap a house before the siding goes on, it supposedly allows moisture to go out but not let moisture in. It does have a particular side that has to be to the outside.

I will do a few blanks in the next week and just put them in the tyvek bags and no dna. Previously i would lose about 30%, i would usually blame that on the variety of species, (we have lots of wood here) the huge swing in temp and humidity here, and the fact that a lot of pieces i do are very figured.

I was skeptical at 1st and purposely left the pith in a large cherry bowl as a test of sorts. It has never cracked and it was the piece that convinced me there was something to the dna process. Scientific reasons aside something has greatly improved my sucess rate.

The bags i use have each had many blanks go thru them and yet they are as clean, dry, and unstained as when i 1st taped them together, no mildew or mold at all.

Here in Mn. we go from brutal cold to hot and humid, a few days ago it was 13 degrees and i still had a few patches of snow, and yesterday it was 83 and sticky.

I will post my results in 2-3 weeks, i am really curious what the results will be.

I cannot take credit for the tyvek bag, a friend of mine who also was having trouble with roughed blanks came up with it, his sucess is also near perfect using the bag and dna.

bob

[Dick Strauss]

Ken,
The speed of drying is the key. In your environment I'd put the drying items in one grocery bag inside of another grocery bag. Just place the item in the first bag and fold the top over 3-4 times. Repeat the process for the second bag. In my environment I use one bag but we have much higher relative humidity most of the year in NW Ohio.

You might also want to contact someone in the Salt Lake City (areas if they haven't already chimed in) since they live in a climate with conditions similar to yours.

By the way, you can re-use the bags if you allow them to dry for a few days before you put your next treausred turning in them.

Good luck,
Dick

[Matt Haus]

Ken,

I have recenlty tried the DNA-24 hr on pecan and some of the heartwood started to crack. I put a little CA on it and it stopped. They were superficial and not on the inside of the bowl. I inspect the bowls almost daily for a few days to make sure they are free of cracks. I have also coated the entire heartwood area on the outside of the bowl with ca and no cracks yet. Perhaps it is shrinking on the inside as is dries and the heartwood has been capped on the outside to prevent moisture loss in those areas. Seems to be working so far. Just my 2 cents.

[George Tokarev]

Your case is one of an occlusive coating which is also an adhesive. I rather think this is the principle behind the polycryl and PVA glue methods. You're slowing the loss at the surface to a rate which can be equalized from the interior, which is what we do with high humidity, regardless of how its created, and you're stopping the contracting fibers from opening up further under tension on the outside surface by gluing them closed.

Even if you can live with the glue-darkened areas, it's an expensive way of drying. Look at those tables of EMC and RH in the Forest Products literature and see if you can't control the cracks by just controlling the humidity some way cheaper. Betting you can.

NB Though I am not a pecan turner, I have seen some which displayed the same sort of random cracks often encountered in dark soft maple heartwood. They're standing stress cracks, not drying stress cracks, and may bite you in spite of your best efforts.