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.


IMG_5022.jpgIMG_5021.jpgIMG_5019.jpg

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.


IMG_5022.jpgIMG_5021.jpgIMG_5019.jpg

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