avoiding warp in wet turned bowls

I'm trying to solve a problem coming from the fact that most of my bowls are turned from sopping wet wood.

I've not had too much problem with cracking but my finished bowls are warping considerably. As an experiment I've started few new bowls using very wet wood and then buried them in paper bags filled with fresh shavings inorder to slow the drying process. Using this process I have placed 5 bowls in bags over the past month and only found cracking in one. However that one had a rather large tenon and a bottom much thicker than the sides. None of the others appear to have cracking in them.

One question is how long to leave the rough turned bowl in the bag. In denver the humidity runs fairly low but I don't know if that should be a factor or not. I've heard anything from a couple weeks to many months.

Another question is how thick to leave the rough turned bowl. This should depend on how much warp I might get as the bowl is drying. Most solutions to the problem of cracking and warping seem to mainly be for cracking.

One solution would be to wait until the logs/blanks are dry before turning them but frankly I don't have enough room to store large logs for years and years.

I ran upon a couple unique solutions for the warping problem and I'm wondering if anyone here has tried them.

Some ausi turners mentioned putting a stick into the roughed out bowl against the grain ends to prevent warp from closing in from that direction. Another post suggested circles cut from MDF.

Any thoughts?

Reply to
william kossack
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The rule of thumb for thickness is 10% of the diameter. This gives room to re-turn after the wood warps during drying. The rule can be fudged if you're familiar with how much the particular wood is likely to warp.

I wait about 6 months on a 10 inch bowl with 1 inch wall thickness. I don't pack the paper bag with shavings unless I'm trying to encourage a bit more spalting during the drying process. Some wait longer, but if it "feels" dry, it's probably ready. Again, experience will guide you after some time. I'd suggest you start with 6 months time, then experiment until you have developed your own "feel"" for the wood by species in your climate.

I've never heard of using a stick. It may work well on some woods, bu will likely encourage others to split. The wood moves during drying to relieve internal stresses that develop. These stresses are what causes splitting. If you keep the wood from moving, the stresses are not relieved, and it seems splitting is more likely.

The purpose of bagging is to slow drying, allowing less difference in moisture content between the outside and inside of the wood. This also reduces stresses by keeping the shrinkage rate more uniform. Packing the wood in shavings further slows drying, as more moisture must move through the paper barrier.

Jim

william kossack wrote:

Reply to
Jim Swank

where are you located? The reason I ask is that if relative humidity is a factor then it can make a difference where you are located. For example, I've lived in places like south texas where the humidity is

90% much of the year. In Denver the humidity is 36% this morning and often in the sumer it is lower.

One of my first bowls (redwood burl) was sopping wet when I turned it. I left it out over night before finishing. By morning significant splits had developed. I therefore use caution about leaving anything that is not stone dry out. It may be that after an initial period of bag drying I can take stuff out but I don't know.

The only experienced local turner I've been able to ask the question about drying uses a kiln to dry his stuff but then again he sells his stuff for $100s

PS In the sumer in south texas sweat drips off of you makes your cloths soaking wet and forms a puddle at your feet. In the sumer in Denver it never reaches the ground and you have to be working hard to know your sweating. Therefore my concern about slowing the drying a bit.

Jim Swank wrote:

Reply to
william kossack

You could try Eli Avisera's way. When he turns a wet bowl or hollow form, he drills an 8mm hole through the base having taken a 10mm 'plug' of the same wood from scrap.

When the bowl is dry, drill out the distorted 8mm hole with a 10mm drill and inset and glue the plug. It really does cut down a lot of the distortion.

Eli's website is at

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He is a brilliantturner from Israel and no, he is not my uncle nor does he pay me tosay how good he is. Kindest regards

Paul >I'm trying to solve a problem coming from the fact that most of my bowls

Reply to
Paul Loseby

Bill I like to turn stuff that feels as if I stand in the shower when it goes round, similar to your description of sopping wet. There are some weird and wonderful ways of preventing warping but the world wide tried and turn method is to wet turn to a thickness of 10% of the diameter, seal the end grain and let dry for about 3 months to a year so the warping is done and finish turning can be performed on a dry blank. See my web site under

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some more info.

Reply to
Darrell Feltmate

Well, duh! Have you deliberately ignored all talk about the LDD solution to your problem?

Reply to
Leif Thorvaldson

Hi William, My thoughts while reading your thread:

  1. Is warp just an incipient crack?
  2. Are shakes, warps, cracks, splits, and splinterings basically different or are they stops along a timber's natural drying cycle that we consider to have gone wrong? Mother nature may not think it went wrong. :)
  3. You can't generalize about wood any more than about people. Too much diversity, even in the same log or even in its parts. Where grown, time of year harvested, how sawn, where being dried are just a few of the variables that plague us..
  4. Actually, it's the diversity that we prize.
5, Obviously there is no best way to dry wood or we would all be using it. The unique solutions that you mention are just as likely to work as many others.

You asked for any thoughts. You didn't stipulate that they had to be politically or botanically correct... or dish washer safe! Arch

Fortiter,

Reply to
Arch

I'm in Northwest Arkansas, probably warmer and more humid than your area. Still the difference is likely less than between a garage and a basement. That's why I say to pick a rule of thumb to start with, then adjust as your experiences indicate.

Jim

william kossack wrote:

Reply to
Jim Swank

I was waiting for the high priest of LDD to weigh in..

Jim

Leif Thorvalds> Well, duh! Have you deliberately ignored all talk about the LDD solution to

Reply to
Jim Swank

I had thought about LDD but only remembered it for avoiding cracking not warp which for many seemed to be a seconary problem.

By your duh! you say it will solve problems of warp?

Leif Thorvalds>Well, duh! Have you deliberately ignored all talk about the LDD solution to

Reply to
william kossack

I am just mortified that this group of answerers didn't even consider suggesting "The Way" to this suffering turner who must deal with the fickleness of green wood. Buy ya books, buy ya books and all ya do is eat the pictures! *G*

Reply to
Leif Thorvaldson

I was looking for generalities. My current batch of free wood is some siberian elm and some hackberry. I also have some aspen and russian olive in small diameters.

This saturday I'm going searching for more local free wood.

Its all a process of learn>Hi William,

Reply to
william kossack

============================================= William,

2 or 3 things to look at.
  1. Wall thicknes 1/10 of Bowl diameter is one "standard"; turn to final shape when dry.
  2. Dryness can be determined with a weight check taken as it dries. When the weight stabilizes, it's reached equilibrium for you location.
  3. Microwaving is also touted by some as a quick dry solution. Check RCW archives for MANY details.
  4. Turn to final shape while wet, let it warp and call it a "feature"

Ken Moon Webberville, TX

Reply to
Ken Moon

Nobody has mentioned the microwave. I hesitate to because I'm such a newbie my ideas change from day to day. But I have been zapping almost all of my bowls and vessels and all are turned very green. If they are turned to a uniform thickness and fairly thin (1/4" or less) then I get very little warping or cracking. The only bad cracking I've had is when I turned end grain, with the pith in, and left the base thick. I guess that's an invitation for problems no matter what you do.

If you want a perfect bowl, turn to about 1/2", zap, then re-turn.

I've found that anything much thicker than 1/2'' just doesn't get dry in the middle no matter how much you zap.

I use O'Donnel's method--4 min. at 40%, wait to cool, then repeat. At

1/8 to 1/4 inch it takes 4-6 cycles. 1/2 takes a whole bunch of cycles.

Earl

Reply to
Earl

I have privately emailed Mr. Kossack "The Treatise," so he should shortly be on the path of rectitude! *G*

Reply to
Leif Thorvaldson

Hackberry and the elm I have obtained locally both move a lot during the drying process. Both woods spalt readily in this arrea, and become much more attractive in doing so. While I wouldn't particularly suggest spalted wood for a salad bowl, you might set a few pieces aside. I don't have aspen or russian olive available, but i've seen some nice things turned from russian olive on the net.

Jim

william kossack wrote:

Reply to
Jim Swank

interesting but then I would have to clean out the food spatters from when my teenagers nuk stuff uncovered;-)

dos the microwave pick up any smells from the wood?

Earl wrote:

Reply to
william kossack

I'm blessed with a basement, so 3/4-1" thick on a 9-12" piece is pretty much the way I go. I spin the shape up to throw as much water as possible, then set it to dry in open air until I no longer see wet on the surface. This to keep from mildew in woods prone to it.

Only then would I coat, If I coated any more, which I don't because it seemed to grow mildew,and no change in shrink, therefore in split. I also tried the cross-grain brace, end grain brace,and circles. Every one promoted splitting, in my opinion. Never lost so many roughs. Back to my original method,which keeps them low in the basement for a couple-three weeks,then on to the shelf until I turn again. I have tented them in newsprint, worked fine, and bags the same, though you really need to change the paper or bag a couple times early on or get mildew problems. I hate to fuss,so the present system is what I use. If you're in a _really_ dry climate, you might consider a big box with modest venting where you can set a batch. Wet below, dry above, move as required, and that is a reasonable substitute for a basement at my house.

When they start to deform, they can be moved up, or taken from under cover, as they have decided to relieve tension by gentle rather than catastrophic movement.

SNIP

Reply to
George

thanks

denver many times gets down to 10-20 percent humidity >I'm blessed with a basement, so 3/4-1" thick on a 9-12" piece is pretty much

Reply to
william kossack

Reply to
George

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