Pith?

[Dan Gill]

I'm new to turning, and I've picked up only bits and pieces of info here and there. I seem to recall reading that you can't use the pith of a log. Is that true? In other words, if I have a log 5 inches across, can I turn a piece that has the pith at the center? Do I have to take the log and saw it in half down the middle, then turn pieces of each half? Is there also some portion of the sapwood that would be advisable to wast? Is this dependent on species?

Thanks for your help.

[Cecil Arnold]

Dan, FWIW, there is nothing worng with sapwood in some woods, depending on the wood. It can very often give your work character. Cut the pith out, it is where cracks begin. Depending on the log, you can lose from 1/2" to maybe 1 1/2" from the center of a log when you remove pith. You may want to check Bill Gumbine's web page as I think he has some pics on preping a log to turn.

[Dave Smith]

Well actually you can leave the pith in if you want. I have done a few pieces with the pith left in to test the alcohol drying method. I will have a piece of vine maple in the AAW Symposium instant gallery that has the pith in the sides. One side had no cracks around the pith. The other side had a few cracks because the center was rotten and extended past the pith. When finish turned there were 3 very small cracks that left that are all but lost under the lacquer finish.

The piece was hollowed through an opening left from a rotten branch. It was rough turned to 5/8" then soaked in alcohol over night then wrapped and dried per my procedure for 3 weeks. The finished piece is 5/16" thick with a small hole where the rot went past the outside of the bowl. My pictures of the piece are not good so I don't plan to post a picture until after the symposium.

You can also turn a hollow form using the whole limb with the pith in the bottom. I have successfully turner many pieces this way using the alcohol method for drying the piece.

You can find my web site in the in the members list. There is a link to an article on alcohol drying that should answer all your questions. If not feel free to email me.

Good luck.

Dave Smith

Starting to melt in the MO heat.

[Raymond Overman]

For pieces like salad bowls, hollow forms, etc. the pith can present problems during the drying process that causes cracks. Most turners I've met prefer to remove the pith before turning by the previous posts methods or turn it out thus eliminating the problem.

That being said, natural edge forms where the diameter of the log defines the diameter of the bowl in an end grain orientation require that the pith be left in the piece. It's important that you take precautions to limit the air flow around the piece until it has reached equilibrium and is dry or you'll see cracks form. The alchohol method may help in this process.

The best thing to do in my opinion is experiment. If you lose a bowl or two, you'll understand the stresses that certain orientations can cause and adjust accordingly.