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How To Turning Green Wood


Woodturners have an endless supply of wood from the urban forest. Just let your friends know you want some and they will keep you supplied. Wood is also often available from gardening or tree grooming services.

Select a chunk of fresh cut wood that strikes your fancy. Crotches, burls or other interesting parts of a tree can give you a rewarding turning experience when the piece is finished. Don't be afraid to turn wood that is not straight grain.

Bring the wood to your shop. If you do not intend to turn fresh cut wood within a day or two (less in hot weather, more time in winter is OK) be sure to store in a dry cool area. Seal the cross cut ends with "log seal" or thick latex paint. A cross cut log, fresh cut from a tree must be split the length of the "pith" if it is not turned within a few days. Stress cracks will ruin most logs in a short time. These cracks will begin at the pith in most instances. However, split the length of the pith will usually prevent all but a few end grain checks. Do not cut the wood into a bowl blank (cylinder) until the day you intend to turn the wood. Checking will surely ruin a bowl blank that sits unturned for long.
Turning a bowl blank is easily done by first screwing the bowls top side of the blank to a faceplate. Turn the bowl bottom to fit a chuck or flat for gluing on a "waste block". Rough turn the outside shape of the bowl as well. Take the bowl blank off the faceplate and mount it to the chuck or waste block. The new Polyurethane glues are great for attaching a waste block to wet wood. The waste block can be screwed to a faceplate as soon as the glue is dry. Rough turn the inside of the bowl leaving about ¾"-1" wall thickness. Once shaped, remove the rough turned bowl from the lathe. Wrap in a towel and place in a plastic bag (photo to right, bowl unwrapped from towel). Twist tie the plastic bag closed. Now the drying begins.

There are several methods of drying the rough turned bowl. I first used the towel/plastic bag method described below. The last couple of years I have found coating the rough turning with "log seal" is as good or better than the towel/plastic bag method. Why the towel and plastic bag? The towel is used to soak up the moisture coming from the drying wood. The plastic bag then traps the moist towel environment around the rough turning preventing spot drying which causes checking and cracking. OK now you have a wet towel and a rough turned bowl in a plastic bag. Keep in mind the general rule of air drying wood, "wait a year for each 1" of wood thickness for drying". The rough turned bowl is ¾"-1" thick so it should dry in a year or less. The towel and plastic bag slow the water loss to prevent cracking and excess warping. That's your goal.
Drying the Wood
One problem with some wood is mold growth Every month the plastic bag needs to be opened, wet towel replaced with a dry towel and the plastic bag closed again for another 30 days. As the months pass it will be noticed that the towel is less wet at each monthly change. At each towel change examine the piece for warping, checking or any other change in shape. Little change should be seen. If there is change there is little you can do about it. Just be sure the towel is in place and the plastic bag is closed tightly.

One problem that shows up with some woods is mold growth (photo to left, white mold on Sweet Gum, red and black mold on Box Elder). Usually the mold is not a serious problem as most of the rough turned piece surface where the mold is will be removed with final turning. If the mold bothers you, try wiping the turning with a weak bleach solution at each towel change.

At about the 6th month, the towel should show no noticeable wetness. If this is the case the bowl can be left out in a cool dry area to finish drying. For the next month, check the bowl at least weekly for cracking or warping. If none is shown, finish turning the bowl at the turners convenience. If cracks or warping start, quickly put the bowl back in the towel and plastic bag for another month.

Turning hollow vessels from green wood can be done without the "towel/plastic bag" procedure if the wall thickness is ¼" or less. Don't expect a symmetrical vessel though. One can turn bowls and trays also without slow drying methods except the final product most likely will not be symmetrical as well. Some woods are very stable and won't change shape much when drying quickly. Elm and myrtle are very stable, walnut tends to distort. Oak may develop cracks as well as distort during quick drying procedures.

Turn the hollow vessel exterior to the final shape. An effort should be made to prepare the exterior surface so that only final sanding is necessary. Next hollow the vessel to the final desired wall thickness. Allow the vessel to air dry for a day or two. Perform the final sanding on the lathe before the vessel distorts too much.

Bill Tarleton
8/28/02
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