Not all what its cracked up to be... Turning a green bowl and then drying.

[mark ahlenius]

Hi folks,

I recently cut up 4 blanks from a cherry log I had on my driveway (wintertime too). I sliced out the pith area of the log and then did my best with my chainsaw to make some round blanks each about 11" in diameter. The blanks were free from any checking or cracks as far as I could see. I recently turned 2 of these down to a "rough cut" bowl which was oversized for the drying process. Then I put Anchor Seal on the grain ends of the turned bowls. I put them in a paper sack and let the start to dry. One of them has been drying for about 2 weeks and when I took it out to look at it tonite, its cracked (see pix). The crack does not run all the way through but looks significant on the bottom side of the bowl.


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I am looking for any advice to save these (doubtful) but more importantly, what can i do in the future to help prevent this?

thanks much!

'mark

[Steve Eure]

One of the things I do when drying green wood is to put it into a paper bag with the wet shavings. Packed tightly seems to help slow down the drying process. I usually leave them for weeks, upwards of 6-8 or longer, checking occasionally.

[John Keeton]

When I turn green I leave them about 3/4” thick or more and completely cover the exterior with anchorseal, including the rim. I don’t coat the interior so it dries from the inside. Your bowls dried from the inside, but also the outside. When the exterior dries it shrinks, but is restrained by the still wet interior. That forces a crack.

[Jack Lilley]

It's the only way I turn. I coat the whole bowl with anchorseal, then on a shelf to dry. I rarely lose a bowl to cracks but when I do it's usually cherry.

[mark ahlenius]

One of the things I do when drying green wood is to put it into a paper bag with the wet shavings. Packed tightly seems to help slow down the drying process. I usually leave them for weeks, upwards of 6-8 or longer, checking occasionally.

Ok thanks, I can try that for sure.

'mark

[mark ahlenius]

Thanks Jack, much appreciated. will try that.

One thing I noted was when I took my last one off the lathe last night, it already had a small crack on the bottom which was not there before.

'mark

[mark ahlenius]

Thanks John

all great advice!

'mark

[David Walser]

Mark -- You've received a lot of great advice. Allow me to add a few comments: First, what works for one turner in one part of the world may not work all that well someplace else. The type of wood, the local climate (or micro-climate), whether the wood is kept in a conditioned space, and even the time of year when the wood was cut, all affect drying. Here in Arizona, if you cut down one of our few trees in summer, the wood will be dry before the tree hits the ground. Okay, maybe that's a (slight) exaggeration. But, the point is wood dries in Arizona more quickly than in, say, Maine, or Kentucky. So, what might work for me most likely won't work as well for you -- unless you're also in Arizona. So, take the advice you've received and try it out. Some parts of it may work better than others. Keep what works and find a method that works in your part of the world. (You can speed this process up by talking with turners who live near you.)

Finally, you're not going to find a perfect method. Some blanks will crack no matter what you do. As you turn, you release some of the internal stresses of the wood, which may cause it to crack. A similar thing can happen when you rip a board on the table saw. The internal tension within a perfectly straight and flat board hold it straight and flat, but, when the board is ripped, the board twists and cups. No drying method, no matter how good, will prevent all cracks. Set your expectations accordingly and you won't get too frustrated by this natural process.

[Kevin Jenness]

Checks can propagate unseen along endgrain farther and faster than one might think. It's good practice to coat the endgrain of your logs as soon as possible after felling. When cutting out a turning blank, cut off any visible end grain checks, then cut off another inch and whack it against something solid to see if there's an unseen weak line. If so, keep cutting back until you reach sound wood. Rough turn the blank right away or put it in a plastic bag or anchorseal it. That may help prevent some failures due to checks that are in the wood but not initially visible.

I've had pretty good luck with local cherry, but I've been told by others it's problematic. Apple has given me a number of failures. David's comments are good- you are going to have some clunkers. You will have to experiment to find the best method for drying roughouts given your climate and the species you work with. For what it's worth I have mostly followed the method you described, but I may try John Keeton's suggestion of coating the entire outside.

One other suggestion is to do the initial drying in a low stress environment- cool, not too dry or windy. down on the floor if in the shop rather than up high. Starting the drying process in a well heated area in winter (in my climate) is asking for trouble.

[mark ahlenius]

Checks can propagate unseen along endgrain farther and faster than one might think. It's good practice to coat the endgrain of your logs as soon as possible after felling. When cutting out a turning blank, cut off any visible end grain checks, then cut off another inch and whack it against something solid to see if there's an unseen weak line. If so, keep cutting back until you reach sound wood. Rough turn the blank right away or put it in a plastic bag or anchorseal it. That may help prevent some failures due to checks that are in the wood but not initially visible.

I've had pretty good luck with local cherry, but I've been told by others it's problematic. Apple has given me a number of failures. David's comments are good- you are going to have some clunkers. You will have to experiment to find the best method for drying roughouts given your climate and the species you work with. For what it's worth I have mostly followed the method you described, but I may try John Keeton's suggestion of coating the entire outside.

One other suggestion is to do the initial drying in a low stress environment- cool, not too dry or windy. down on the floor if in the shop rather than up high. Starting the drying process in a well heated area in winter (in my climate) is asking for trouble.

Thanks Kevin, you described almost exactly what I did. When I got the Cherry Log (within a day or so if it being cut down, I Anchor-sealed the ends. It then sat on my Driveway for perhaps 5 months or so before I cut it into blanks. I did cut back about 4" from the ends until I found "good wood". After cutting the blanks, I brought them inside (basement) and coated them with Anchor seal.

I live in the midwest (Chicago area) - and right now with winter, its been quite dry. So I'll be trying these suggestions to see what works best for me in this environment.

One other question, with the cracks which do not go all the way through, are these blanks now destined for the burn pile, or do you think they can be saved?

thanks much!

'mark

[mark ahlenius]

Thanks David, I really appreciate you taking the time to respond and your advice. Funny stories about AZ. In Illinois, we get the four seasons with varying humidity all the time.

best

'mark

[John K Jordan]

How thick is the wood at the sides and at the bottom? The thicker the wood the more likely it is to crack. Roughed with thin sides and thick bottom is more likely to crack on the bottom so you want the thickness of the bottom the same or less than that of the sides. (Thinner is OK, going out of round from drying is less of a problem on the bottom.) Turned thinner is less likely to crack but tricky to know how thin you can make to have enough to turn round after it warps.

Drying too fast increases the chance of cracking. One paper bag might not be enough if dried indoors in a heated space in the winter. Some people dry by putting the piece in a closed plastic bag then every day take it out, reverse the bag, and put it back in - this can slow the drying considerably. This is labor intensive but I've read of success with it. (If you leave it sealed up for too long it might spalt nicely or rot not so nicely)

I've had better luck when I coated the entire outside of a roughed bowl with anchorseal and left the inside unsealed. Some people have had good results by wrapping the outside (only) with plastic wrap. For both of these the theory is the faster drying on the inside will cause more shrinkage on the inside and keep the outside pulled tighter.

Turner and author Stephen Russell is a big proponent of boiling rough turned bowls. Apparently the heat softens the lignin and more evenly distributes the stresses from shrinking while drying. He said boil at least one hour per inch of thickness. Boiling too long won't hurt anything. In his study the success rate was very high. A gentleman I knew in Peru boiled all bowls before final turning and export. Some of the wood species he used would crack if you looked at them sideways. He boiled in a 55gal drum over a wood fire. Some people use a propane-fired turkey frier. Just be careful the bowl doesn't fit snugly in the vessel or the whole thing can explode catastrophically.

Some people simply turn the bowl to final thickness (thin) without roughing and drying first. The wood will warp but be less likely to crack. Many like the look of a severely warped bowl. I made some like that years ago and left the bark on. The effect was nice.

If the bottom is fairly thick on that one you might be able to cut away the crack.

Btw, some wood species are much more forgiving. Cherry and other fruit woods can be difficult. Walnut and sassafras can be forgiving.

JKJ


Hi folks,

I recently cut up 4 blanks from a cherry log I had on my driveway (wintertime too). I sliced out the pith area of the log and then did my best with my chainsaw to make some round blanks each about 11" in diameter. The blanks were free from any checking or cracks as far as I could see. I recently turned 2 of these down to a "rough cut" bowl which was oversized for the drying process. Then I put Anchor Seal on the grain ends of the turned bowls. I put them in a paper sack and let the start to dry. One of them has been drying for about 2 weeks and when I took it out to look at it tonite, its cracked (see pix). The crack does not run all the way through but looks significant on the bottom side of the bowl.


451838451839451840

I am looking for any advice to save these (doubtful) but more importantly, what can i do in the future to help prevent this?

thanks much!

'mark

[Kevin Jenness]

"One other question, with the cracks which do not go all the way through, are these blanks now destined for the burn pile, or do you think they can be saved?"

From the looks of it the cracks will probably show up in the finished bowl. Only one way to find out.

You can insert a glued spline or dovetail key if you feel the bowl is worth the effort. Some people call them "pewas" and charge more for the repaired bowl.

Heating with wood saves something from the situation. Doctors have to bury their mistakes.

[Don Stephan]

Five months sounds like a long time to let a log begin drying through the bark. As a general rule I try to turn from a freshly cut bowl within a week, with the ends sealed immediately after cutting or ASAP.

And occasionally I will have one walnut bowl crack across the growth rings on the side or bottom out of ten or more.

[mark ahlenius]

Thanks Kevin. for me its all about learning how to correct mistakes or misfortunes with woodworking.

'mark

[Prashun Patel]

Guessing from your pix the prob was too thick a bottom.

I find that large bowls are hard to keep from checking. I theorize that the rim pressure at the top creates a lot or stress at the base. Regardless I have to take care to turn the bottom thin enough. Did you use calipers to gauge the bottom? The bottom thickness + the tenon should be roughly the same thickness as the rim.

If the base is close to the bark, the dominance of the sapwood vs heartwood near the pith might also cause an issue as they seem to dry at different rates.

Last, was this log a trunk or branch. Branch wood is far more likely to check and split than trunk wood in my experience.

[Reed Gray]

Cherry is more prone to cracking than most woods. Other than that, make sure the rim edge is rounded over. If you have a sharp edge, not only will it slice you if you get close to it while it is spinning, that sharp edge will dry more quickly than the rest of the bowl, and that will start a crack. Generally the rim is most vulnerable. This is why many wrap the rim with some stretch film. I have rolls that are about 5 inches wide, so maybe an inch on the inside of the bowl, and the rest down the side. If you are bringing wood in from the outside, that can be a considerable climate change, especially where you are. If you have any shop heat, that adds to the temperature change. If you put the bowls out in the garage after turning, that might help. If not, then put them on the shop floor, which is generally cooler, and make sure there is no moving air around them, even a cardboard box will work. I don't put mine in wet shavings. I do turn green to final thickness, and let them dry and warp. The problem with wet shavings can be getting the bowl moldy, and color stains, which aren't always good. Another method is a paper bag inside a plastic bag, and change the paper bag every day. This works well for Pacific Madrone, which starts to crack before you even get the chainsaw out. Boiling does work, but for me, it is too much work and it muddles the colors together. You can use the cracked bowls to learn how to repair the cracks. Personally, I don't do that, again because it is more work, and I don't feel like I can guarantee the bowls. I expect the repair job to fail eventually. I consider them to be okay for 'art' pieces, but not for daily use bowls.

robo hippy

[Dave Bunge]

I agree with Don that 5 months is a long time to let a log sit before turning. The log loses moisture through the bark and starts to shrink around the perimeter of the log, regardless of what you've done to the ends. If the log is still round (hasn't been split through the pith), there is no way to accommodate the shrinkage, so cracks form.

There's another famous woodturner from TN named John Jordan who demonstrates at the AAW and other symposia. I've heard him state that 90% of the cracks that people get don't happen during drying, but were already present in the wood before they started turning it. I suspect that's what is happening to you, especially since you say cracks are already visible in some bowls before you take them off of the lathe.

I've had good luck storing cherry blanks, as long as they were processed quickly after the log was cut. By "processed" I mean: cut to length (several inches longer than needed to allow room for trimming), split through the pith (or even an inch or more from the pith if there are cracks already present at the center of the log), coated on the ends with Anchorseal Original (another whole discussion is possible on which version of Anchorseal is better) and stored under mild conditions (out of the sun and elements in my garage and with a tarp over the top of the pile to prevent drafts and slow down the drying).

As far as what to do with the wood you have: If you have any blanks left, I'd recommend making smaller bowls (cut away more of the sapwood). Or you can rotate the blank 180 degrees and put it in the orientation you would use for natural edge bowls. You can still make a cut rim bowl from this orientation; it'll be a lot smaller. But it will also contain less sapwood and have a different grain appearance that some people, including me, like better.

As far as drying, here's what I do in the middle of Michigan, perhaps a similar climate to yours: Double bag in paper bags (no shavings), change bags every day or two in the beginning until bags are no longer damp, dry on wire racks to allow airflow underneath the bowl. If I use Anchorseal, which is rare, I only coat the outside. Sometimes I will use CA glue preemptively on the tenon, since it's the part of the bowl which will have the thickest section of sapwood. I'll coat CA on the vertical (endgrain) part of the tenon and across the flat face of the tenon.

Hope this helps.

Dave

[John K Jordan]

...
There's another famous woodturner from TN named John Jordan who demonstrates at the AAW and other symposia. I've heard him state that 90% of the cracks that people get don't happen during drying, but were already present in the wood before they started turning it. I suspect that's what is happening to you, especially since you say cracks are already visible in some bowls before you take them off of the lathe.
...

The famous John Jordan also recommends not cutting the log into pieces if possible. Pieces are more practical for a turner without equipment but do have the limitations mentioned. He said he gets a longer log even if he has to pay to have it delivered. (This could be a way to get your hands on some BIG wood!) He stores the log off the ground out of the sun and doesn't bother to seal the ends. When he is ready to turn something he cuts about 6" off the end, cuts the blank, then turns it.

He has some useful articles on his web site, one may be especially useful for someone turning bowls and such from green wood, including how to section the log for different pieces and effects. He states the most common problem he sees is "Tiny checks become BIG cracks! This article is not new (published about 23 years ago) but the principles haven't changed. "Understanding Green Wood" found here: https://www.johnjordanwoodturning.com/articles-and-interviews.html
(Another good resource is the book "Understanding Wood" by R. Bruce Hoadley, well worth studying by anyone who works with wood - Hoadley is both a craftsman and wood scientist.)

Just for fun, here's a picture of the famous John Jordan at the TAW symposium maybe 11-12 years ago. Doug Thompson (Thompson Tools), the other John, John Lucas, and me. (we do have snow in TN on occasion!)

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JKJ

[Dave Bunge]

The famous John Jordan...has some useful articles on his web site, (like) "Understanding Green Wood" found here: https://www.johnjordanwoodturning.com/articles-and-interviews.html

Nice article. I called him "another" famous John Jordan because you're pretty well known around here and worthy of fame in your own right due to the huge amount of helpful info you've posted. Some things you've recommended over the years that I use, just off the top of my head: 3M green high performance masking tape for sticking to anchorsealed surfaces, storing CA glue in a jar with desiccant to extend the shelf life, retractable Sharpie markers, just click like a ball point pen to expose the marker. And lots of great pictures of well shaped items to emulate.

It would be nice to have enough real estate and heavy equipment to store large logs on my property off the ground, in the shade and in an uncut state. Not too practical for me and probably not for other surburban woodturners. I'll stand by what I said earlier: I suspect the OP's problem is due to cracks already present in the wood before he started turning it. And if he would have cut it into blanks that he moved off of his driveway 5 months ago, he'd have better luck today. (And even better luck if he would have turned it 4 months or longer ago.)

Dave

[John K Jordan]

Thanks for the kind feedback, much appreciated!

Good point about the space and equipment. I don't think JJ has the equipment but pays someone to deliver and set the log in place. I have NO idea how much that would cost but I think it might be expensive if I did it. :) (Actually, now that I have a dump trailer it would be a lot easier...)
I've also heard him and others say a trip to a log dump logs or even to a small sawmill can reap good wood freshly cut from a larger log. I've had people come to my place many times when I have logs I'll gladly cut fresh wood for them to take home. (The book Harvesting Urban Timber by Sam Sherrill, while aimed at acquiring lumber, also writes about acquisition.) And I know a woman who maintains her own log dump and gladly shares with woodturners! She's given me big ambrosia maple, osage orange, cherry, and walnut.

Some other advice for new turners that I've heard from multiple sources: never take home more green wood than you can turn in a week or two! The temptation is so strong to get way too much because, why not, and it's free! Problem is it most eventually turns to firewood. Been there, done that.

I strongly agree with your comment about processing the log sections as soon as possible. I do that often - split the log, then cut around the pith and existing defects to get the largest blanks possible. On some species I avoid the sapwood too. Since I almost always turn dry wood I seal and put these blanks up to dry. I've had people tell me that won't work, it will always crack, but I think that depends on a lot of factors. The success rate for successful drying has been high even for fairly large blanks from some species. The long drying time and the storage space needed is the biggest problem. This is not practical for big bowl turners but medium sized blanks like this one of ambrosia maple usually dry nicely. Eventually!

451896

I mostly cut rectangular blocks for future flexibility, but for those who like to turn small things this processing provides a variety of smaller blanks so there is not much waste. I'm able to provide far more pen blanks than our club's Pens for the Troops program can possibly use. Anyone in this area who could use a tub or two of pen and other small blanks stop for a visit!

BTW, most people probably know this but when processing rectangular blanks on a bandsaw there is an easy way to eliminate those hidden end-grain checks that can grow into big cracks and ruin the blank later: after squaring up the block cut a thin slice from the end (maybe 1/8") then bend it a bit. If there are any hidden cracks the thin piece will break at the crack. I keep removing wood at the end until I'm into solid wood then seal immediately. I hope to do a video (or series) on all this sometime.

JKJ


Nice article. I called him "another" famous John Jordan because you're pretty well known around here and worthy of fame in your own right due to the huge amount of helpful info you've posted. Some things you've recommended over the years that I use, just off the top of my head: 3M green high performance masking tape for sticking to anchorsealed surfaces, storing CA glue in a jar with desiccant to extend the shelf life, retractable Sharpie markers, just click like a ball point pen to expose the marker. And lots of great pictures of well shaped items to emulate.

It would be nice to have enough real estate and heavy equipment to store large logs on my property off the ground, in the shade and in an uncut state. Not too practical for me and probably not for other surburban woodturners. I'll stand by what I said earlier: I suspect the OP's problem is due to cracks already present in the wood before he started turning it. And if he would have cut it into blanks that he moved off of his driveway 5 months ago, he'd have better luck today. (And even better luck if he would have turned it 4 months or longer ago.)

Dave

[Alex Zeller]

I've let maple sit for over a year on the ground. I have a large crotch sitting in a snow bank right now. When i get to it I'll cut the end off and make some blanks out of it. It's a good way to get spalting. Haven't tried it with cherry though. One thing that does happen is the moisture will settle to the bottom near the ground. Whether it's from the sun drying the top part exposed or just gravity pulling it down I don't know. But I try to cut the blanks in a way so they have an even level of moisture so they dry evenly. I also do the paper bag with high moisture chips packed around the bowl.

[Rich Aldrich]

I have turned quite a bit of cherry. I use Denatured alcohol soak for 48 - 72 hours air dry for 1/2 hour the put it in a craft paper bag (grocery store type) for a month. This works pretty good. Fruit wood is prone to crack.

I have made a number of cherry salad bowl sets.