"Turning Wood into Art"

"Nothing is better for a man than that he should eat and drink,
and that his soul should enjoy good in his labor...."
-Ecclesiastes 2, 24

Thursday, January 28, 2010

From Tree to Table, Part 4: Turning a "Green Wood" Bowl

In the preceding parts of this series, we talked about bowl turning techniques that result in the perfectly round  wooden bowls most favored by woodturners today and, perhaps more importantly, by those who purchase their wares(!).  We talked about identifying downed trees most likely to yield usable bowl blanks, how we go about extracting those blanks from the tree, rough-turning and drying our bowls, and finally finish-turning.

But today we are going to talk about turning a bowl from the blank just as it comes from the tree all the way to completion in one fell swoop!  Although we will go into the history of bowl turning in Part 5, it is interesting to note that until the last 50 years or so, wooden bowls were almost always turned to completion from "green" wood.  So, in a way, we're going back in time....

Turning green wood uses almost exactly the same techniques (and safety precautions!) we employed previously. But this time, we will try to anticipate how our bowl will warp and twist as it dries - and adjust our design and embellishment approaches to make that warping and twisting work to our advantage.  We hope (!)

Our first decision is to decide whether we want a "cut-rim" bowl, as described earlier and shown at the top of this page, or a "natural-edge" vessel like the red oak piece on the right, where the bark - or the wood immediately below the bark - forms the rim.  Intended use is our primary consideration, because if we plan to leave the bark in place, the finished bowl almost automatically becomes decorative "art" rather than a utilitarian vessel. (Bark being very fragile.)

That decision made and because our bowl will start to dry while it's being turned, we need to be sure we have enough time to complete our bowl in one session.

Just as described in Part 2, we fix our blank to the lathe and rough-shape the exterior.  (Note that we have not yet completed the exterior shaping.  That comes next.)

At this point, we reverse our blank in the lathe so that the top of our bowl faces away from the headstock. (Several techniques can be employed here.  Each has advantages and nuances that are beyond the scope of this post.  As before, I refer you to the many books on the subject of bowl turning, if you would like further information.)

With the tailstock still in place for safety, we refine the exterior.  We wait until now to refine our exterior for two reasons: first, because of almost certain miss-alignment when we reverse the bowl and secondly, because our bowl has started to dry and is no longer perfectly round.  We expect our bowl to warp and twist over the coming weeks as it dries, but we do need a round exterior at this point so as to be able to apply whatever decoration (beads or coves) we might wish to use(see footnote.)  Once our bowl is again running "true," we take a fresh (read very sharp) bowl gouge and make a series of light cuts to remove any remaining tool marks, along with any grain that might have "torn-out" during the roughing process.  Once the surface is as "clean" as we can get it, we now sand our exterior very lightly with a foam- or sponge-backed sanding pad (or power sander.)  The key at this point is to minimize pressure, friction and the accompanying build-up of heat, which will only hasten the drying process and give us a less-than-satisfactory result.

We next re-sharpen our bowl gouge and hollow-out our interior.  Timing is now especially critical, because our bowl is drying very fast and starting to warp.  Again, I will refer you to the above-mentioned books for specific techniques, but our objective is to hollow-out our bowl as quickly - and SAFELY(!) - as we are comfortable doing.

Once we have the interior shape and wall thickness to our liking, we again take a freshly sharpened bowl gouge (or specially designed bowl scraper) and clean-up any interior tool marks or torn grain. (We can now apply any desired interior decoration as well.)

As a next-to-final step, we finish-off our base using an appropriate technique (see reference books for ideas - of which there are many.)

Lastly, we apply a liberal coating of pure walnut oil and wrap our new bowl in a paper bag for a week or two to control the initial drying.  At the end of that time, we set our new masterpiece in a reasonably controlled environment to enjoy as it completes the drying process.

Again, I thank you for your attention.  Woodturning techniques are not "etched in stone."  Each craftsman (or -woman) varies these techniques to suit individual style or preference.  And so I invite you to post any questions, comments or suggestions.

Next time: A Brief History of Woodturning.

Until then....

Footnote(1): Depending on wood species, the amount of moisture in the wood, and how we oriented our blank on the lathe, our bowl can be expected to warp in either a nice symmetrical pattern - or a wavy asymmetrical manner.  Both can be quite beautiful.  So we want whatever decoration we apply to accentuate or compliment the final shape.  (For example, the red oak bowl shown above was formed with two fairly dramatic exterior coves, which accentuate its now mildly oval shape.) 

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