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Hi all,

I worked on a black walnut bowl for my brother, working all evening and then quit for the night. The next morning I came back and there were a number of splits in it. I filled some of them with black ebony, to see if it would enhance it...I didn't think it did. (I hope the pictures will show, and the troubles I've had)

My questions are these: 1) What can I do to prevent this from happening again (as I have loads of black walnut)? 2) If they crack what is a better "filler" to put in black walnut? 3)What is the best finish for Black Walnut??

Again thanks to all of you and your knowledge,

Rex

PS..The granddaughter is awesome in her fairy wings!!
 

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The wood is cracking because the outside is trying to dry and shrink while the inside is still wet and large. You have to stop the drying. I put a plastic bag over my turnings to keep them at the state they are in. I do this even if I go into the house to go to the bathroom. It's also a good idea to spray water on the turning occasionally if you not very fast at hollowing. This keeps the outside as wet as the inside so it will dry evenly.
When you finish hollowing put it up to dry in a place without direct sun and no air movement. this will allow it to dry more slowly.
 

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As the other replies mentioned, this is caused by the wood being "green" which is a term meaning it has a lot of moisture (water).

Wood contains two types of water
a) free water which exists between the cells. Different species/pieces have different amounts of free water. If you see water droplets when turning, typically this is free water. This will not cause as much dimension change as the bound water.
b) bound water in the cells. This takes time to evapourate. The bound water will evapourate until it reaches equilibrium with the water content in the surroundings. The shop while you are turning, the room where the piece will eventually be displayed. As the bound water evapourates, the cells will shrink. If the shrinkage is not consistent across the wood, then it will check/crack. The slower the loss of moisture the better the chance to minimize checking/cracking, but some is common.

As you turn you will expose more of the cells and so will lose moisture faster.

The sap wood is likely to contain more moisture in the cells than the heart wood so there is more to potentially lose, and the more moisture which is lost, the more the wood will shrink resulting in checking/cracking.

This is not unique to walnut.

If you are lucky the cracking will not weaken the bowl. Sometimes it can, so you need to watch carefully.

Epoxy is a good filler for large cracks, but if the wood is continuing to lose moisture, the epoxy will not prevent further cracking.

Some people mix epoxy with ground stones, some with pigment.

A commercial product I like is In-Lace. I have the turquoise. Makes for some interesting colour contrast. Not cheap.

http://www.packardwoodworks.com/Mer...Store_Code=packard&Category_Code=surdec-inlay
 

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I have this happen all the time I use thin CA as I go to stop the cracks somewhat. They usually grow a little more so I apply a bit more CA. While it is still wet i lightly sand the area to add saw dust to the mix then let it dry and continue turning.

I have found that turning thin as fast as I can helps a lot. Once I have it turned I place it in a closet for 3-4 days then back to the lathe for a finish sanding. Yes it will warp some but I can still get the sanding done.

John and Dave laid out the best ways to try and prevent this or to save it.
 

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If you don't fill the cracks they will mostly close up once the inside of the wood moisture content matches the outside. They are still there and dangerous but they will often close up to the point you can fill them with thin CA. Spray water on the outside and keep it wet (I use an old windex bottle). Then hollow out the inside. If your lucky the outside cracks will stay small or even close up as the inside dries.
Filling the cracks now just keeps them that large. CA glue won't hold a vessel together if it decides to explode on you. Epoxy does a better job for this but if the cracks are large enough it's best just to reduce the size of the vessel and get rid of the cracks entirely. then keep it wet and finish turning it. Better to be safe and have a crack free piece than to try and salvage one with cracks. Just my opinion but you never see a professionally turned piece with cracks.
 
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