Black Walnut

[Bill Holt]

Mid-September I helped remove a black walnut.  The pith was removed and the halves were sealed.  Pandemic hit and I had time to rough turn 12 bowls.  They ranged from 12 to 14 inches across and 6 to 9 inches high.  Most are 1.25 inches thick or thicker.  All were sealed and stored in my shed.  Last week I noticed two had major splits in the sides.  What did I do wrong??????????????

[AHill]

Which "halves" did you seal? End grain or face grain?  Did you just rough turn and store in a dry shop? Even after rough turning, I'd seal again. You may not have waited long enough to let the blanks stabilize before rough turning.

[MichaelMouse]

Mid-September I helped remove a black walnut.  The pith was removed and the halves were sealed.  Pandemic hit and I had time to rough turn 12 bowls.  They ranged from 12 to 14 inches across and 6 to 9 inches high.  Most are 1.25 inches thick or thicker.  All were sealed and stored in my shed.  Last week I noticed two had major splits in the sides.  What did I do wrong??????????????

 I assume face grain, so a couple things come to mind. 

First, mind the heart checks when you rough.  They will open as the wood contracts no matter how much glue you filled them with.  Study the cross grain when you cut, and make your radial or diametric cuts to eliminate them.  Don't know if that's your problem, but if it is cracking up on the rim, don't try to include a check. 

Second, don't make dog dishes.  Round or taper to the bottom so there isn't a broad area of cross-grain to contract and find a weak spot .  Early wood contracts much more than late, so don't leave long runs of early wood to pull against curving latewood rings.  Also, you left too much wood thickness in the walls.  At 1 1/4 plus in smaller diameters, you are begging for what produces radial checks in the round log.  Might get away with it in larger, properly shaped stuff, but why bother, since wood cuts easier when green, and cures faster when thin. 

I don't seal anything, personally.  Tried anchorseal when it first came into vogue, and got mildewed maple as a result.  So I turn about 3/4 to 1" thick, put 'em on the shelf and leave 'em.  Can't remember the last one that cracked on me.

[Bill Holt]

Allan, I seal every surface except the bark.  After rough turned I seal the whole bowl before putting it on the shelf up-side-down.  I've not had issues on 10" and smaller; 10" to 12" are turned about 1" in thickness, smaller are closer to 3/4".  12" to 14" my luck goes South.

Michael, I'm not an educated turner, self taught except for two classes.  The cracked bowls are bell shaped and the cracks occur on the side below where the flare out begins.  I live near Dallas, it gets hot.  On two different occasions I've had roughed bowls crack in less than 18 hours (I believed, because they were not sealed).  Some years ago, here on the brain trust, a "rule of thumb" suggested the thickness of green rough turned bowls should be about 10% of the width.

I really, really appreciate both of you taking the time to help me!!!!!!!!!!!!!!

[Arlin Eastman]

Bill

I do not know as much as the others on the drying part but if you seal the whole thing how will it dry.

I am thinking like the straw affect you have to seal the straw ends and let the sides allow it to dry.  Straw ends in along the grain so that needs sealed.

If I am incorrect please anyone correct me.

[MichaelMouse]

Allan, I seal every surface except the bark.  After rough turned I seal the whole bowl before putting it on the shelf up-side-down.  I've not had issues on 10" and smaller; 10" to 12" are turned about 1" in thickness, smaller are closer to 3/4".  12" to 14" my luck goes South.

Michael, I'm not an educated turner, self taught except for two classes.  The cracked bowls are bell shaped and the cracks occur on the side below where the flare out begins.  I live near Dallas, it gets hot.  On two different occasions I've had roughed bowls crack in less than 18 hours (I believed, because they were not sealed).  Some years ago, here on the brain trust, a "rule of thumb" suggested the thickness of green rough turned bowls should be about 10% of the width.

I really, really appreciate both of you taking the time to help me!!!!!!!!!!!!!!

Well, one inch per inch is baloney, as is one inch takes 1 year to dry.  Then again, it's also not the heat, but the Relative Humidity which determines the end MC and the rate of loss.  I was stationed at Beale, and learned to coddle a bit in bag or box for a week or two.  Currently just set them on the concrete for their first week - basement in winter, garage other.  I also allow free air access to both interior and exterior by keeping them on their bottoms. 

It's your shape that's the main culprit, seems to me.  Ends up with the bottom too wide, like the dog dish, so consider faster rounding or taper to divide the contraction stress between down - dropping the long grain sides of the piece - and squash, which splits ends, especially if you also go thick.  Remember that contraction along the grain is virtually nil, contraction across around 10%, which is also the contraction percentage between latewood rings.  What kills you are long lateral distances across the smiles. 

Oh yeah, I was thinking about the last time I lost some roughs.  American beech, and bulbous.  Before that, #%&*@ madrone.

[EightFingers]

Make the bottom slightly thinner than the sides. I never had a problem with walnut.