Sunday, May 26, 2013

Ever Put a Wooden Bowl in a Microwave Oven?

Hi Everyone,

One of the enduring difficulties in turning unseasoned wood is the drying that occurs when a bowl or platter is turned. The turning exposes the grain of the wood and any water that is inside of the wood evaporates away. Sometimes, if the grain dries evenly, the bowl will retain it's shape and not crack. But if the grain dries unevenly cracking and distortion of the sides of the bowl or the bottom of a plate can occur.

One way to get around this is to turn an unseasoned blank several times, each time removing a little more wood and then wrapping the bowl blank in heavy paper so it will dry slowly and hopefully evenly. And you've seen me do this many times. It can take 4-6 months for a large bowl to dry out this way and a long time for a project to come to completion.

Another way to dry out a bowl is to place it in a microwave oven and heat the wood up. This drives out the water in the wood and can speed up drying from months to 30 minutes. That's the good news. The bad news is that it can cause the wood to rapidly dry out and distort, ruining the piece.

I've never tried it before and since I have a small block of linden wood in the shop I decided to go down and turn the linden block into a natural edge bowl and to then take it into my kitchen and microwave it.

So here's what I did:

Here is a photo of the linden block. It's half of a large branch that I've had for about 1 1/2 years or so and so I'm going to turn it into a natural edge bowl. This is a bowl that still has some of it's bark left on the edge:

This is about 90 minutes later. This type of turning produces a saddle-shaped bowl and you can see the shape beginning to form:

Here is the bowl after I've hollowed it out. This took approximately an hour of turning. The wood is soft and even though I've sanded it, it's still has a ragged surface in places:

Here you can clearly see the saddle shape and the bark on the edge:

Here is the bowl after it's had a session in the microwave. It's hot to the touch and very damp at this point but I don't see any cracking or obvious distortion. I've placed it on my bread rack to dry and I'm going to put it in front of an open window. I'll check back on it later today.


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