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

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/fp.../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.....