Turning Archive

Subject:
Delamination of roughed bowl blank

Mike Stafford
A friend of mine who is relatively new to turning came to me with a problem. And after seeing it and discovering what he did I don't know what happened and I don't know what the can do to fix the problem.

He had rough turned an 11 inch cherry bowl to about a uniform 3/4" thick everywhere except in the area of the spigot on the bottom. Then he dried it in the microwave. After each drying cycle he weighed the bowl so he would know when it was dry. He figures that when the bowl no longer loses weight it is as dry as he is going to get it.

He dried it in the microwave 61 times until it stopped losing weight. He then let it sit for a couple of days to acclimate. After acclimating the bowl measures about 11 1/4" end grain to end grain and 11" face grain to face grain.

When he went to mount it back on the lathe some of the face grain on one side of the bowl was delaminating. I am sorry I don't have a picture but perhaps you can visualize a nicely shaped 5" tall by 11" diameter bowl. On the outside curve on just one of the faces which has exposed face grain there is a section of the face grain which is delaminating along the grain line from about 1/3 of the way from the bottom to the rim. At the bottom the wood along this grain line feathers to almost nothing but at the top where it intersects the rim it more than 1/4" thick.

I hope that makes sense. I have no idea if the bowl can be salvaged. I am fearful that the entire big section of face grain will pop off if he has any trouble with his tool control.

I don't have any experience with microwave drying of green wood but 61 cycles cannot be good for the wood. Any of you use a microwave to dry your roughed bowl blanks? How do you go about it?

Any suggestions on what he might be able to do to salvage the bowl/

He lives way, way out in the country and he doesn't have any form of internet access so he can't post a picture.

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