Drying Green Blanks?

[Ken Schleman]

I’m searching for info on how many green blanks after reaching the usable driness are unusable due to warpage.?
Im getting 2 out of 10 that are firewood due to being warped beyond useable.

[Steve Eure]

Give more detail on your drying methods. I generally green turn and either put them in a paper bag with the shavings for several weeks or if I have enough to fill my small kiln, I'll use that to dry and still about 3 weeks to dry. I usually only loose around 10%.

[Leo Van Der Loo]

I’m searching for info on how many green blanks after reaching the usable dryness are unusable due to warpage.?
Im getting 2 out of 10 that are firewood due to being warped beyond useable.

You are doing pretty good if you loose only 2 out of 10 drying without splits and just get only some warpage on them.

It also takes a lot longer to dry whole blanks rather than rough turned pieces, and a whole lot less splitting if dried after roughing the blanks, or turned to finish.

There is one or two people that dry their wood, but it usually is just small thin pieces of wood and I bet they get ends splitting still, as my wood does not behave any different than their or your wood.

I would recommend you try turning green wood and then drying it.

[Ken Schleman]

Thanks guys, I rough turn my bowls then put them in a paper bag with sawdust. I have a couple old freezers with light bulbs in them, the heat is controlled by a thermostat.
i guess I’m not getting an excessive amount of firewood from what you guys say.
Until recently Elm and Maple were my choices , but I discovered that the landfill near me stacks up tree logs for firewood that they give away. The selection is like a wood turners candy store, so next year I’ll be able to select more stable wood than Elm and Maple.
Thanks for the help guys.

[Thomas Canfield]

I turn a most of my pieces from green wood turned to 10% or slightly more diameter thickness and of late have been packing in double paper bags with shavings. The pieces do warp but almost all can be returned thin from the warped thick walls. A few have to be "shortened" to have the outside not meet the inside up at the rim due to major warpage. I do try to dry some of the 15% D pith slabs without pith or larger end grain stock by sealing ends and stacking to air dry.

[John K Jordan]

Thanks guys, I rough turn my bowls then put them in a paper bag with sawdust. I have a couple old freezers with light bulbs in them, the heat is controlled by a thermostat.
i guess I’m not getting an excessive amount of firewood from what you guys say.
Until recently Elm and Maple were my choices , but I discovered that the landfill near me stacks up tree logs for firewood that they give away. The selection is like a wood turners candy store, so next year I’ll be able to select more stable wood than Elm and Maple.
Thanks for the help guys.

Your first post confused me! From the first message and this one it seems you mean drying "rough turned bowls" rather than "green blanks". To me and many others, a green blank is a solid chunk to be turned, not usually dried.

If so, and they are not cracking or splitting but are just warping too much so you can't turn them roun , can you not just leave the walls thicker when roughing? They will take a little longer to dry but must should survive. I usually coat the endgrain on the outside (or the entire outside).

I don't turn many bowls from green wood, but when I do I generally leave the walls pretty thick. After my first mistake of roughing too thin, I can't remember one being too warped to get a finished bowl. If anything, I err on the side of too thick (but that just builds patience :)).

Remember the larger the diameter, the larger the rough-turned walls need to be. Check resources such as the Wood Database for T/R ratios and such. It also helps to cut the blank from a large enough log to keep away from juvenile wood and in some cases, hardwood/sapwood boundaries. BTW, I learned a lot about wood and what it does when drying from R. Bruce Hoadley's book "Understanding Wood" - highly recommended.

Since I almost always turn dry wood I process a lot of green wood into turning blanks and dry them. I do successfully dry a lot of green blanks, some of them "large", and success without checks and cracks is not impossible. Note that "large" is relative and can mean different things. When I get time I'll write up some notes on drying blanks in case anyone is interested.

PS, I see by the time I got back to finishing this Thomas wrote basically the same thing. (but far more succinctly!)

JKJ

[Dale Bonertz]

I will add a caveat to what John wrote. The coating of end grain works in a more humid environment or location. I don't see where you live so places like Arizona, Colorado and etc. that have low relative humidity you are better off and will be more successful coating the entire blank. It will slow drying a bit more but as John states it is just patience. Real world maybe an extra month to air dry, no difference in kiln drying.

[Ken Schleman]

Thanks Guys. The info is very useful. The coating the rough turned bowls i did not know.
The bowls I had to throw away or put in the wood stove measured 12 3/4” by 11 1/2” just to far out to get a bowl .

[John K Jordan]

I do most of the drying in my conditioned shop which is dryer than ideal. But one thing I find helpful is to begin the drying outside then bring the pieces inside after a month or more, depending on he species and the temperature. If left out too long in warm weather the powder post beetles can get a start. Starting it outside seems to get a lot of water out of the wood before bringing it into dryer conditions.

I do seal the end grain well immediately after cutting as well as sealing any wild grain such as burl, crotch figure, and the heartwood/sapwood boundary in certain species (such as dogwood). I also use thickened Anchorseal - this seals better than two coats of normal Anchorseal. To thicken I simply put in in a container open to the air and let it dry out a little.

JKJ


I will add a caveat to what John wrote. The coating of end grain works in a more humid environment or location. I don't see where you live so places like Arizona, Colorado and etc. that have low relative humidity you are better off and will be more successful coating the entire blank. It will slow drying a bit more but as John states it is just patience. Real world maybe an extra month to air dry, no difference in kiln drying.

[John K Jordan]

Thanks Guys. The info is very useful. The coating the rough turned bowls i did not know.
The bowls I had to throw away or put in the wood stove measured 12 3/4” by 11 1/2” just too far out to get a bowl .

I seal with Anchorseal, an emulsified wax that dries to a clear wax. Some people cover the outside with shrink wrap. The idea is to slow down the outside drying to prevent cracking. However, I don't think sealing will change the final oval dimensions much so the roughed-out wall would still need to be thick for large sizes of some species.

Just curious, on the bowl you mentioned what was the species and the original wall thickness? I think a list of the rough thickness people have found to work for various species and sizes would be helpful.

Another way to minimize degrade is boiling. Boiling used to be a widely used method (because it worked!) but I haven't heard much about it in a long time. Turner Stephen Russell did and wrote about his extensive experiments with boiling about 20 years ago and reported a success rate of better than 96 percent with thousands of bowl. Boiling can speed up drying but more importantly it can decrease loss from cracking an warping. I believe warping is minimized when the lignum is softened by the heat. Stephen provided detailed instructions but unfortunately his web site is no longer available, although it can be accessed through the internet archive. In a rare moment of wisdom I downloaded some of Stephen's web articles in html form - very useful - I could write some basic steps when I get time if you want to try this method. When I did it I used a turkey fryer. (Warning, there is safety issue to learn before using a turkey fryer for this.)

A woodturner in Peru once old me that he sold a LOT of finished bowls internationally. They boiled every rough-turned bowl in 55-gal drums over wood fires. He also boiled unturned wood blanks with success. He sent me some large blocks of exotic (to us) species that he warned me MUST be boiled or they would crack into pieces! Another example is madrone - every madrone burl blank I've bought had been boiled to prevent crazy warping, almost expected with madrone. Turner Graeme Priddle told me all the madrone he uses is also boiled. (Some people like to turn madrone wet to final thickness and let it warp like crazy.)

Another thing to do is to turn in the end grain orientation rather than the normal face grain orientation. This may take a pretty large tree to get a useful large blank unless you do like many and include the pith in the center. When turned with the end grain up warping while drying can be far less, especially if you keep the juvenile wood away from the edge. This is the way lidded boxes are made, both because of the initial warping is less after roughing with green wood but even more because the seasonal movement is far less. One good reference is Raffan's book on turning boxes.

Another thing to do with an excessively warped rough-turned bowl is to carve it! I've seen some excellent examples where the blank was turned to a finished surface inside and at the rim, then carved or textured on the outside after drying. The other John Jordan is famous for his carved hollow forms turned green then carved when dry. If carving is not your thing, you might give or sell turned blanks to people who carve but don't turn - an artistic collaboration opportunity!

JKJ

[Ken Schleman]

The bowl that warped very bad had 1” walls, but managed to warp beyond usefulness.

[Ken Schleman]

I guess it’s back to boiling my rough cut bowls, I would rather do the boiling than to waste the rough turned bowls

[Jeffrey J Smith]

Ken - I turn a lot of Maple and Madrone - Madrone warps incredibly, so anything I want to twice-turn gets boiled. Maple does warp, but more predictably and definitely not as much as the madrone. Boiling helps, but it's a pain to get the rig setup so, unless there's a lot to rough out or I've got some madrone to rough at the same time, maple just gets dried on the shelf. I've seldom had a dried maple blank that couldn't be turned, regardless of the warpage. Leaving a generous tenon to grab - even if its severely oval - helps. It only has to hold long enough to turn a recess (short ledge) in the inside so I can turn the roughout around and true up the tenon. This has become standard practice for me on those pieces that I twice turn. Never seen maple warp so badly that it couldn't be salvaged...at least the Big Leaf we have around here.
I do have a chunk of locust roughed out on the shelf that has sat there for a few years now - it's warped to the point that when I do put it back on the lathe, truing it up will require eliminating at least half the remaining mass. Hardly seems worth keeping it, but it looks kind of cool on the shelf - all weird and floppy. Besides, I like the look of locust, so I'll get it down one of these days to finish and see what's left.

[John K Jordan]

... Leaving a generous tenon to grab - even if its severely oval - helps. It only has to hold long enough to turn a recess (short ledge) in the inside so I can turn the roughout around and true up the tenon. ...

I'll have to try that method sometime. I usually jam the rough turned bowl and hold it with the live center get the best adjustment on the piece then to true up the tenon. But even after that, turning a recess inside would have some advantages for working the outside and base. (I usually prefer to finish turn the outside first.)

This is making me want to dig into my neglected stock of roughed out bowls, some drying now for 8-10 years. Think they might be dry yet? :)

[Roger Davis TN]

Take a look at this on YouTube:https://m.youtube.com/watch?v=DaaTbDTUsg0 Some types of cat litter contain silica gel which is a desiccat (a hygroscopic substance used as a drying agent). They can even have color that turns when full. Then just bake in oven at low temp. till dry. That's the packets found in Rx bottles etc.
Have not tried it yet but sounds great. Roger

[John K Jordan]

Take a look at this on YouTube:https://m.youtube.com/watch?v=DaaTbDTUsg0 Some types of cat litter contain silica gel which is a desiccat (a hygroscopic substance used as a drying agent). They can even have color that turns when full. Then just bake in oven at low temp. till dry. That's the packets found in Rx bottles etc.
Have not tried it yet but sounds great. Roger


You can get indicator desiccant at Amazon. https://www.amazon.com/gp/product/B000OUXA2Q/
I bought several of these, at first to recharge some air line dryers without paying for the expensive disposable cartridges. Now I also use them to keep CA glue from setting up. Since moisture can activate the glue and moisture can go through most of the plastic bottles, I keep the glue in a sealed container with some desiccant.

Since I took this picture I found a much better/larger container in the housewares section at Walmart. It has a rubber seal and latch so I don't have to unscrew a lid each time.

398161

The desiccant beads turn change color from blue to pink as they pick up moisture. I recharge them by pouring into a tray and heating in a toaster oven I keep in the shop.

One problem I can imagine is it might take a LOT of desiccant to pull all the water out of a bowl. Desiccant beads alone might dry the wood too fast, but the cat litter mixture might be perfect. To recharge in the oven takes a long time.

JKJ

[Ken Glass]

This has always been my choice of drying for green wood blanks and I have rarely had any checking or splitting.
1. I rough turn green blanks to 1/10th of diameter.
2. Immerse blank in Denatured alcohol for 24-48 hours depending on size.
3. Remove and let surface day for 1-2 hours.
4. Wrap in brown paper and tape up tight like a mummy and weigh.
5. Weigh piece weekly until weight loss starts to slow .
6. Weigh daily until I reach same weight 3 days in a row.
7. Finish turn and apply Finish treatment of choice.

[John K Jordan]

[QUOTE=Ken Glass;2873052]This has always been my choice of drying for green wood blanks and I have rarely had any checking or splitting.
1. I rough turn green blanks to 1/10th of diameter.
2. Immerse blank in Denatured alcohol for 24-48 hours depending on size.
...

Something that might speed the drying even more, between your steps "1" and "2". The other John Jordan put compressed air inside a freshly hollowed form and an amazing amount of free water bubbled out of the pores. Removing a lot of the free water that way would let give the bound water a path for more hasty escape.

Doing this with the hollow form only needed one hand to make a seal against the opening but for a bowl I think a flat piece of mdf or something with a small hole for the air nozzle, perhaps with a layer of foam to seal against the rim would work. This method might not work as well for a thick roughed wall for some species though, would be interesting to try.

JKJ

[Ken Glass]

John,
I have been known to blow compressed air in and around the blank/HF to remove surface moisture before wrapping the blank as well. Once wrapped up I let the DNA do the moisture extraction.

[Karl Loeblein]

From my experience... Boiling rough turned bowl can help prevent some cracking, but it might not prevent much of the warping. If you have a wood that warps a lot then consider turning the bowl more twice. If the wood is freshly cut then make your first rough turning thicker than 10% to be on the safe side. Then rough turn again (one or more times) as it starts to dry/warp, but remember to keep bowl sealed between turnings (i.e. Anchor Seal, How Wax, School Glue, Bag, Box, etc..) to lessen cracking. Eventually you'll figure out which woods are Ok to twice turn (cherry & walnut) and which ones might need to be turned more than twice (freshly cut oak or persimmon). Bonus: You'll experience less bouncing and better control the more times the bowl gets turned.

Personally, I don't always have time to rough turn my green wood the day it's cut. I've gotten decent results coating my green blanks in hot wax (using a large electric skillet) which then gives the wood a chance to harden off and warp a little before I get to the initial rough turning.

[John K Jordan]

From my experience... Boiling rough turned bowl can help prevent some cracking, but it might not prevent much of the warping. ...

I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. Many types of wood are pliable enough to allow bending them after steaming, and green boards off the sawmill can be constrained from warping by stickering and drying under weight, could a freshly rough turned bowl be dried while the rim is prevented from freely moving?

For example, if the rim were jammed in a sturdy hole it just barely fit into and then dried slowly as normal it seems to me it might take the "set" and stay round enough to finish turn even if the walls were thinner. While I originally imagined stout metal ring, other methods might make more sense, at least for a test.

One idea is to cut a circle out of a piece of plywood that just fit around the rim. The plywood would need to be big enough to be strong, but based on my experience drying stickered lumber I'm not convinced the force would be extremely high.

Who knows, maybe constraining the movement might cause other problems such as encouraging cracks, but can't know until tried. Has anyone tried this? If not, a test wouldn't be difficult for someone who turned a lot of green bowls. Just turn two close to identical from the same log, omit the boiling, then constrain one and not the other, and dry as usual. If that proved to have problems, repeat the test with three more roughed bowls, one boiled and constrained, one boiled and not constrained, and the third not boiled as a control.

Anyone want to try this? You could be rich and famous. :) it works, you can put my name with yours on the patent! (Ha! Just kidding, I have enough patents. But even if it does, I'd be surprised if someone else hadn't thought of this and wrote about it it decades ago.)

If constraint did work, I can envision a jig that had adjustable jaws that could be snugged up against the rim, say six or eight, and bolted down. The jaws could be snugged periodically as the rim shrunk while drying. A more robust version could have a screw jack on each jaw.

JKJ

[Glenn C Roberts]

I use hose clamps. There isn't much spring, so they need to be tightened periodically.

[John K Jordan]

I use hose clamps. There isn't much spring, so they need to be tightened periodically.

That sounds too easy!

Do they prevent bowl from going out of round?

[Dave Bunge]

I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. ...could a freshly rough turned bowl be dried while the rim is prevented from freely moving?

For example, if the rim were jammed in a sturdy hole it just barely fit into and then dried slowly as normal it seems to me it might take the "set" and stay round enough to finish turn even if the walls were thinner.... One idea is to cut a circle out of a piece of plywood that just fit around the rim.
JKJ

Interesting idea. But the walls are going to shrink inward, so you'd need something inside the bowl pressing out to keep the bowl from going oval.

So instead of a hole, cut a plywood disk sized to jam tight inside the rim. You'd have to cut some holes in it for circulation so the bowl could dry. Or maybe, instead of a disk, you could just wedge a small board inside touching opposite sides of the rim at the point where it wants to shrink the most. That would be 90 degrees from where the pith falls on the rim.

[John K Jordan]

I wonder if constraining from the inside could cause cracking on the outside as the wood shrinks.

I'm imagining that even if a bowl constrained on the outside did go a little oval when shrinking, perhaps the warping might not be as crippling as it would be otherwise. I like your idea of using wedges but perhaps on the outside, driving them in a little further as needed.


Interesting idea. But the walls are going to shrink inward, so you'd need something inside the bowl pressing out to keep the bowl from going oval.
So instead of a hole, cut a plywood disk sized to jam tight inside the rim. You'd have to cut some holes in it for circulation so the bowl could dry. Or maybe, instead of a disk, you could just wedge a small board inside touching opposite sides of the rim at the point where it wants to shrink the most. That would be 90% from where the pith falls on the rim.

[Glenn C Roberts]

Hopefully you can see the "defects" (?) on the base of this 10" unfinished butternut dog dish. I used a hose clamp on the base to stop the crack progression and warping in that area. It worked perfectly. I also clamp the base of end grain bud vases and that also works. Clamps on the rims of bowls I have not tried because I like the warping, but it's easy enough to do.

[Karl Loeblein]

I've wondered about the possibility of minimizing warp or "unwarping" a warped bowl with steam or boiling. Many types of wood are pliable enough to allow bending them after steaming, and green boards off the sawmill can be constrained from warping by stickering and drying under weight, could a freshly rough turned bowl be dried while the rim is prevented from freely moving?
...

Would keeping boards from warping by 'stickering and drying under weight' bind up some stress in the wood? Just thinking these internal stresses could be reactivated by cutting the wood or a change in humidity. In other words, is it better to leave bowl unconstrained so no stresses are introduced, or constrained in order lessen any warping? Agree, this would make an interesting experiment if someone had time.