Checking/cracking while twice turning bowls

[Dean Center]

A question for Leo. The brown paper bag technique you advocate and others also is simple and works well in your environment. Would a tightly closed cardboard box accomplish the same ends, slow down the drying just like a paper bag?

In the Buckle of the Great Northwest Power Belt, a box should work OK as long as it's sized right for the contents.

 

[Bernie Kopfer]

Bernie, using a cardboard box is not the same or works the same, but it can slow down the drying as there is only a limited amount of air in the box and with enough bowls or smaller box, the air in it will get saturated and so slows the drying, but that is where the similarities stop

With the brown paper bag the initial part is the same, the air gets saturated, a paper bag can also be closer to the turnings size, so less air, now the bag will absorb some moisture, and the turning can loose some more moisture, than the paper bag will have the air surrounding the bag take some of the moisture from the bag, and the bags inside air will give again moisture to the bag, the turning will then be able to loose some moisture again and this all keeps repeating till the moisture levels are the same all around.

The cardboard is not able to do the same as the brown paper bag, but it could maybe loose some moist air if the flaps are not fully closed, though it would be much harder to have a consistent process, as with the brown paper bags use.

Thank you Leo, that is exactly the information I was seeking. Where I live in Eastern Washington the humidity is low year around and painfully low inside in the winter. I'm going to try the brown bag method with the next batch of green first turned bowls. We have access to lots of fruit apple wood around here and also cherry. PVA coating has been my way of slowing down the drying process with very good results, but your pictures of apple wood bowls is really impressive!

 

[Leo Van Der Loo]

Thank you Leo, that is exactly the information I was seeking. Where I live in Eastern Washington the humidity is low year around and painfully low inside in the winter. I'm going to try the brown bag method with the next batch of green first turned bowls. We have access to lots of fruit apple wood around here and also cherry. PVA coating has been my way of slowing down the drying process with very good results, but your pictures of apple wood bowls is really impressive!

Bernie, use what works for you, I know the brown paper bags should work for just about everyone, as for Apple wood, I love turning it, it turns so well and the colors are all over, pretty stable after it is dry, I've made some larger boxes with it and no problems with them in 15 years.
Here are some Applewood turnings

 

[Doug Freeman]

Where I live in Eastern Washington the humidity is low year around and painfully low inside in the winter. I'm going to try the brown bag method with the next batch of green first turned bowls.

Just be aware that it may take a little experimentation to get it right. The evap rate is a function of the temp/humidity difference from inside to outside the bag/paper. This difference may change summer to winter, depending where you store the bags (I keep mine in the house, where I use a humidifier in winter, and the house temp/hum doesnt change much year around, so the drying rate is pretty consistent). The heavy brown paper bag is what is needed (I want to say its “70 lb stock” but not certain), and in your low humidity area, you probably need 2 bags.

For larger turnings (wont fit in a big) I use heavy kraft paper, sold sold as paint drop cloth at the box store, and tape closed. The bags and drop cloth are reusable many times.

 

[Dean Center]

Thank you Leo, that is exactly the information I was seeking. Where I live in Eastern Washington the humidity is low year around and painfully low inside in the winter. I'm going to try the brown bag method with the next batch of green first turned bowls. We have access to lots of fruit apple wood around here and also cherry. PVA coating has been my way of slowing down the drying process with very good results, but your pictures of apple wood bowls is really impressive!

Fruit woods are highly prone to cracking, so Leo's results are extraordinary. There's no way I could get fruit wood to dry safely here in the northern Rockies with just a bag. I coat the outside with wax emulsion plus the bag and also try to put in as stable an environment I as I have, and it will still crack. Don't pull your hair out if you lose some apple blanks. It's beautiful wood and wonderful to turn, if you can get it to dry intact. If they clear the old trees after they're fully dormant, that will help, too.

 

[robo hippy]

Hmm, haven't tried the box method yet, but don't see why it wouldn't work. The idea would be that the inside takes some of the excess moisture, but doesn't take all of it, so you get the piece surrounded by air that is higher humidity than the outside the box air. I have heard of using feed sack bags, but now days, most of them are plastic rather than the heavy paper ones. I would guess that the old gunny sacks could also work. Drying is at least as much of an art as any turning is. Every wood and every environment is different! I guess that is part of the fun/frustration of turning, learning, through trial and error, what will work, at least what will work most of the time...

robo hippy

 

[Noah Peters]

Has anyone tried the paper lawn and leaf bags sold at Lowes?
The description says that they are treated as to withstand moisture and cold.
This would slow down the drying more but would this also increase the chance of mold and other problems.
I am just curious because the bags are bigger so you could potentially stack bowls inside so you would need fewer bags.
it's something I was mulling over and was wondering if anyone else has done something like this or how they have done it differently.

 

[Dave Landers]

Has anyone tried the paper lawn and leaf bags sold at Lowes?
The description says that they are treated as to withstand moisture and cold.

I get them from Ace hardware usually, but yeah I use those. Don't know about any treatment (never looked). I see them as basically just huge, double-walled, paper bags.
I load up the bag with a bunch of bowls and shavings. When it's full, I tape it closed, add the date (etc) and slide it under the bench for several months.
I don't get mold but it's pretty dry here.

 

[Doug Freeman]

Paper lawn and garden bags - they have a moisture barrier layer between paper layers. Yes they work quite well, but are best used as Dave states above, many items or 1 very large item. I only use them for large items. I prefer “smaller batch drying” in smaller bags so I can easily weigh to know when dry. Just preference though.

They work very well for cut blanks vs using liquid sealer to reduce cracking.

 

[Ken Dambrosio]

I've been having a significant problem with checking and cracking while twice turning bowls of late. I dry rough turned bowls in my furnace room which now in the Northeast is warm and very dry. I've been placing the wet bowls in paper bags (thanks Leo) and drying them on wire shelves. This seems to have worked well as the bowls warp but largely haven't checked or cracked while drying. They dry very quickly, sometimes even in just five weeks. The problem arises when I jam chuck the dry bowl (against a four jaw chuck) and begin turning the outside. After my first or second pass checks or cracks begin to appear seemingly out of nowhere. Generally they only get bigger as I take subsequent passes. This has occurred mainly with black cherry and walnut which I've read are prone to cracking. Today it happened with a sugar maple bowl (Anchorsealed) that's been drying for six months. This wasn't happening in the summer when the furnace was off. I haven't heard of anyone else drying bowls in their furnace room which is a warning flag. My thought has been it's a kiln like environment so in theory should work well. The dry bowls I've been turning are 12 to 15 inches in diameter and I'm jam chucking against five inch jaws. My best guess is I'm drying too quickly and/or it's too much stress removing them from that dry environment to immediately turn in my cooler and more humid shop. Any ideas, thoughts or suggestions are greatly appreciated!

And for years, after I rough turned a blank, I would just take a large brown paper bag, staple it closed, and just put it under my workbench, and leave it there for a good 8 to 10 months for most Fruitwood and Nutwood. (note : it is on a cement floor, not on top shelve)

 

[Rip Littig]

My wife is about to get rid of several old but washed sets of sheets. Has anyone tried wrapping once turned bowls in sheets and/or towels to dry? In theory it should work if wrapped several times by an entire sheet. Just curious if anyone has experience effectively wrapping with cotton as opposed to paper.

 

[robo hippy]

I haven't heard of anyone doing that. It should work. The wrapping is for creating a mini environment where the bowl dries slowly. Wood dries too fast = cracks. Wood dries too slow = rotting. Give it a shot and let us know!

robo hippy

 

[Don Wattenhofer]

Just a guess but I would think that a sheet would cling to much of the outer surface and selectively wick moisture, where as the brown paper bag will not cling and more effectively create the "mini environment" that the bags do so well.

 

[Marc Banka]

I think that wrapping in sheets would slow air movement, a bit, and would slow drying, a bit. Good sheets, well most sheets, breathe. Their design is to let moisture through.

keep some of it for applying finishes, etc.

 

[hockenbery]

My wife is about to get rid of several old but washed sets of sheets. Has anyone tried wrapping once turned bowls in sheets and/or towels to dry? In theory it should work if wrapped several times by an entire sheet. Just curious if anyone has experience effectively wrapping with cotton as opposed to paper.

It’s worth a try however it likely would wick the moisture away too quickly.
might need some support frame to minimize cloth contact with the wood.
the paper bags provide a humidity chamber that evens out endgrain and sidegrain moisture lose rate.

 

[John Tisdale]

For over 15-yrs I've been boiling "roughs" which have all been hollow-forms up to 22" diameter.
Like you, drying/cracking/warping was of huge concern - I found the below article by Stephen Russell and it was a game-changer.
If you start boiling, let me know - I've got a few additional tips (like not being stupid)

https://www.richmondwoodturners.org/pdf/handouts/boiling_wood.pdf

 

[Lou Jacobs]

John,
Thanks for this article. I recently had a load of holly that I was eager to be extra careful with, both to preserve the color and size, since I don’t often come into larger (8-11”) pieces of holly. On advice I got here, I tried boiling the wood, but it was rough blanks (discs), not rough turned bowls. I boiled for an hour per inch, mostly three plus hours. Then coated endgrain and they are now in either paper or a large cardboard barrel I use for slow drying. So far, so good. I’ll see how it goes in a couple more months.

 

[Doug Freeman]

If you start boiling, let me know - I've got a few additional tips (like not being stupid)

Hey John, what are your tips? I’ve been contemplating giving boiling a try.

 

[John Tisdale]

Here is the rest of the procedure that has worked for me on large hollow-forms:
- On the initial turning, cut the outside to gallery ready - the profile needs to be "spot on" - the second turning a few month to a year away should be more a "rounding" than a "correcting"
- On the initial hollowing, and assuming a 20" max diameter, I cut to around 3/4" thickness ramping to 1.25" at the max
- While I use sash-weights, boiling bowls will take some creativity
- After the boil time, LET IT COOL ON ITS OWN - when cool, immediately take the piece(s) to the final drying set-up (paper bags / large cardboard boxes and dry very slowly to 20%-MC - from 20% to around 6% you can be more aggressive. Gene Weingert's white paper on drying can be pulled from the Lignomat site
COMMENT: BOILING a) minimizes cracking, b) dramatically speeds drying time, and c) does nothing for warping

Doug: Above are the primary tips - send me your cell and I'll give you a call

 

[JeffSmith]

I’m in a relatively wetter part of the country - the Pacific Northwest. I’ve been boiling our local woods - big leaf maple, madrone and alder for a couple of decades. On those occasions when I left the roughed blanks in the pot until cool enough to unload I had serious problems with mold as they dried. I was taught to unload the pot at the end of the day while it’s still hot - after the blanks had boiled for at least a couple of hours. Stack the hot bIanks on edge and let them cool (generally leave them until morning). When fully cool, stack bottoms up on wire shelves with good air circulation and leave them to dry.

As long as I follow the process, cracks have been virtually eliminated And mold is not an issue.

 

[dbonertz]

I find these topics fascinating. It really exemplifies the challenges we all face with our climates, homes, wood species and moisture content of the wood once we receive it. All the methods mentioned above work, except the one you have been trying . I've used many of them and have had great success with them. One consistent message you should be learning by now is slower the better for a good outcome, unless you have a kiln. Whatever you decide is best for you may depend on your storage situation. Bagging for instance takes more space due to stacking issues. Cardboard boxes take a fair amount of space, however you can put many blanks in a a bigger box with chips and stack boxes up so save a bit of space.

Actually drying blanks in your furnace room will work if you seal the entire blank with your favorite wax emulsion product. Stack the blanks with stickers between them open bowl side up. Slide a large plastic bag (garbage bag) over the stack and weight the end that touches the floor so no air can freely move around the blanks (you can throw wood chips around bottom, kinda messy for a basement though or duct tape down but not the entire edges - you want some air). At the beginning flip the plastic garbage bag inside out every three to four days or so. Do that for several months or flip it more if you see mold wanting to take hold (don't worry so much of the cotton type mold). The heat from the furnace will be somewhat like a kiln (heat source) and the garbage bag will act as a moisture control. Do that for several months (2 to 4) and then more often until about dry. After about 4 months you can stop sealing the bottom edge where the bag meets the floor. When you think the blanks are really close to being dry then take the bags off totally for a week to month to finish. I wouldn't use this method if you have plenty of room for the other methods, I only bring this up if you are limited and the utility room is your best storage option. This method is also more work and you have to really pay attention.