What's up with the cracking?

[Jim Burr]

I have a nice Curly maple (from MIike Smith) vase, about half dry, on the chuck and was unable to finish it. Just the outside shape was done. I tossed it in the DNA bucket for a week. I'm on limited/no movement for 6 weeks so I wrapped it up in newspaper and put it in the cabinet about a week ago and checked on it this morning....some minor checking 1/16" wide here and there.
Would I have been better off to wrap it in plastic wrap and leave it on the chuck? Should I have bored a hole in the center prior to soaking? Inquiring minds need to know!

[John Keeton]

Jim, I am not a guru on the DNA method - having only done one piece!! But, my guess is that the piece soaked up the DNA, but can only dry thru the one side. The bulk of the wood is still wet with water. The outside surface is drying significantly faster than the inside, and the whole idea behind any drying method is "even" loss of moisture.

[Roger Chandler]

This is a good thread! A lot of folks do a trial and error [mostly error :eek:] sort of guessing game with drying..........especially newbies. I agree with John K. that the point is even drying to the best degree possible........in your case, a hole in the center may have saved it.....depending on how thick it was when you left off the turning process.

Maybe you can fill those cracks and voids with some epoxy or thick CA glue and some filler like sawdust or some other medium that would contrast. Might make for a good save and unusual finish.

[GLENN THOMAS]

Jim,

I was watching a Richard Raffan video not too long ago on turning boxes. He would rough out the outside as well as the inside, then throw them aside to dry. I guess this works for him and it seems like it should apply to your project as well.

[James Combs]

From what I have read and the discussions I have seen on this forum it is almost a requirement that when rough turning then drying (no matter the method) the inside has to be removed and typically the inside is left exposed to the atmosphere with only the outside covered with paper or plastic. Typical wall thickness is 10% of the diameter. The theory is that if the vessel dries from the inside first the stresses tend to "pull" the walls together as the inside wall drys faster then the outside. If the outside dries faster the the walls are pulled apart and cracks result.

In your case if there was no time to turn the inside it may have been better to put it back in the DNA or at least in a sealed container of some sort so that no drying took place until you could get to the inside.

[David E Keller]

The other option would be to paint the outside of the form with something like anchorseal... Even a coat or two of finish might slow down the outside drying enough to prevent some cracking. I hope you can salvage it.

[Jim Burr]

Oh yeah...it's keepable. I'll try to get out in the morning and rough hollow the inside, peel a little off the outside and then dry it again and see where it goes...Mike has plenty more wood!

[John Keeton]

In your case if there was no time to turn the inside it may have been better to put it back in the DNA or at least in a sealed container of some sort so that no drying took place until you could get to the inside.Jim, for what it is worth, the last Claro piece I did - the Copper Necklace - was in the DNA for nearly a month!! I forgot about it being in there. It didn't seem to bother it at all.

[Leo Van Der Loo]

You should think about WHY wood splits, wood does not split because it is wet or dry, it splits when there the wood dries and there becomes a difference between one part of the wood and another part of the wood that will cause a stress that is bigger than the wood is able to withstand.

A thicker piece of wood that is allowed to dry too fast will shrink on the outside while the inner part is not shrinking as fast, when the outside becomes shorter in circumference then the shortcoming will be made up by splits.

If you had wrapped your piece with something that had not allowed the wood to dry on the outside, it would not have split.

Plastic wrap would do it, Anchor seal would also have done the job, even though it does let moisture out, but very slow and would be fine for a short time at least

So next time wrap it in a plastic bag, it will give you some time before the wood will start splitting, just be aware that this might get mould to grow, but that is not a big problem for a few days or weeks, HTH

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[Jim Burr]

That's happened to me John. I've always been told that the amount of time in DNA isn't important...how long out is!

[Don Nurmela]

I am not convinced yet that the DNA soak thing works. I have rough turned about 15 bowls leaving 10% or more of diameter for wall thickness, soaked 24 hours or longer, wrapped the outside with brown paper bag, taped the rim, left the inside open, and stored upside down with ventilation available to the inside. Most of them have sat for 2-3 weeks and all of them have cracked to some degree, some through wall. All have warped, alot of them to the point that round is no longer an option, basically firewood.
I just tried coating with a sealer inside and out after DNA bath. I have now resorted to turning wet/frozen to completion including finishing and hoping for the best. Any suggestions?
The wood is maple, freshly cut and rough turned frozen and directly into bath.

[Leo Van Der Loo]

I roughed 14 White Ash bowls the beginning of December and bagged them in Brown Paper Bags, they are dry and without any splits in the wood or even the knots, just the bark inclusions on two bowls opened up.

I dry all my bowls in brown paper bags, that are placed at a cool spot without heat or any draft, and I have very seldom splits drying bowls, though I seem to be talking into the wind :rolleyes:
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[Don Nurmela]

I started with using the brown paper bag method and the roughed bowls split wide open, must be the maple?

[Jim Burr]

I roughed 14 White Ash bowls the beginning of December and bagged them in Brown Paper Bags, they are dry and without any splits in the wood or even the knots, just the bark inclusions on two bowls opened up.

I dry all my bowls in brown paper bags, that are placed at a cool spot witbhout heat or any draft, and I have very seldom splits drying bowls, though I seem to be talking into the wind :rolleyes:
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Rest assured Leo, your advice is well heeded. The paper bag supply in the valley may dry up soon! The same should hold true for HF's and the like then, yes?

[Leo Van Der Loo]

Yes Jim, slowing the drying so the inside can keep up with the outside will prevent the stress in the wood getting so it has to split :).

[neil mackay]

I have a nice Curly maple (from MIike Smith) vase, about half dry, on the chuck and was unable to finish it. Just the outside shape was done. I tossed it in the DNA bucket for a week. I'm on limited/no movement for 6 weeks so I wrapped it up in newspaper and put it in the cabinet about a week ago and checked on it this morning....some minor checking 1/16" wide here and there.
Would I have been better off to wrap it in plastic wrap and leave it on the chuck? Should I have bored a hole in the center prior to soaking? Inquiring minds need to know!

Jim, Basically theres not a one method that "does all" I find DNA works well with some and not so with others. One thing I have found is that I have to turn the piece very close to the finish size. Rough outs with thick walls dont really work to well as a rule. Then let the surface DNA dry off 15-20mins and store away in paper.

I routinely wrap my partially finished work left on the lathe in a plastic bag if I am going to finish it off with in a few days

[Dick Strauss]

Jim,
Your climate is much drier during most of the year than Leo's area. Leo's storage spot may also be somewhat damp or have less draft leading to slower drying. There are just too many variables for a one-size-fits-all solution (other possibilities include existing cracks prior to drying, wood defects, type of wood, etc...).

If it were me, I'd start with at least two paper bags or maybe three to slow the drying in your climate for most of the year. This time of year with all of the rains, you may find that two work better. You'll have to experiment with number of paper bags, DNA or none, and storage areas with less or more draft to prevent cracking in the long term. One other thing, wet the wood with mineral spirits or something similar prior to drying to better make sure you turned away all existing cracks. You want to slow the drying enough to prevent cracking but not to the point of the piece getting too moldy.

Good luck!

[Ken Whitney]

Leo's point about different parts of the wood having different responses to drying is exactly right. Whatever drying method is used needs to have moisture loss balance the different rates of shrinking.

I've had pretty good results with DNA soak followed by wrapping the outside of the bowl with stretch wrap. I'm in Sacramento, and the humidity is chronically low. Since the outside of the bowl typically shrinks more for a given amount of water loss than the interior, this seems to slow the moisture loss from the outside relative to the inside. No (or way fewer) cracks.

The paper bag method didn't work very well for me.

Ken

[Jim Burr]

So I go out this morning and un-wrap the vase and not one single crack, check, split...nothing! Of course I'm ecstatic…jumping with joy…metaphorically of course. Not wanting to waste my good fortune, I’m coring it out as we speak. Now the question remains, since the DNA has displaced the water, placing the piece in a bag as the remainder of the alcohol evaporates should be sufficient?

[Leo Van Der Loo]

If this is the vase with the splits in it you were talking about in the fist part of this hread, then the split you can't see now are still there of course, it this is another vase without any splits in it then the bagging should help it dry without splitting, just make sure you place it in a COOL place WITHOUT and heat and or draft.

As for the suggestion that my place would not be very dry, this time of year with the cold air outside that has very little moisture in it and that air gets into our houses , where we then heat this air, the result is air that is as dry or drier than the desert air, summertime brings high humidity here wintertime gives us very dry air in our house.

The thing with the brown paper bag is that it becomes a small place with saturated air from the wet wood, and it will dry as slow as the moisture can leave the brown paper bag, so it is important that the bag is in an area where it does not dry fast like when air moves over it, also the cool air takes moisture up slower than warmed air.

Two bags is too slow for me, one bag works just fine for me, but I do have a room in my house that is not heated and has no air movement if I close the dampers, and that is the place I dry my bowls.