Designing
Turned Bowls

Notes from the book "Turned Bowl Design"

By Steve Reznek

The recent discussion of style and form and my commitment to write an article made me go back and get out my well-thumbed copy of “Turned Bowl Design”. First let me say that this article is a synopsis of Richard Raffan’s book, with a few of my own observations. I would hate to be accused of unreferenced plagiarism or sued for all the profit that I will make. Raffan is a “production” turner whose skill makes useful objects into things of beauty.

He repeatedly emphasizes a couple of points. Before I get into some of the more specific or technical details, let me stress them:

“It is easy to produce a bowl that, by virtue of its rich color and/or wild grain patterns, will draw gasps of admiration. I have also heard many wood turners talk of revealing that which is hidden in the timber. This is all very humble, but it too often reflects a willingness to rely on quality of wood to carry a poorly designed or badly executed piece. Because all wood fades and mellows with age, I focus my attention on form and tactile qualities. Eventually they will be all that’s left, and if these aspects are found wanting no one will bother to keep the bowl.

If you reach beyond the gloss of attractive grain and a polished profile, there’s a good chance that your bowls will not only feel good and function well, but grace the eye when not in use.”

Before I get into design aspects let me inject another quote form the book. In the introduction he talks a little bit about pricing and therefore gets into how long it should take to turn a bowl once you have the wood. Are you ready for this? “My formula works well on sizes greater than six inches. I simply multiply the diameter by the height and arrive at the approximate time in minutes. For example: six inches times three inches gives 18 minutes.”

The technical guidelines that follow need a big caveat - what looks and feels good is good, no matter how many of the rules it violates. If you think the Golden Mean generates too steep a bowl decrease the ratio of the height to the diameter.

What should the profile of the bowl look like? The answer is that there is no answer. Usually it is bad to make the arc a section of a circle. What Raffan calls an asymmetric profile, i.e. the curvature changes, will be more interesting.

The Golden Mean ratio - 1:1.618 - has somewhat magic mathematical properties. But the important point is that is seems to “look right”, at least to many people. If the diameter is 1.6 times the height, the bowl will look well designed. But this will look good if the sides of bowl are vertical or recurved to more than vertical at the rim. And the bottom of the bowl is horizontal.

 (Note: The book does a heck of a lot better at illustrations than I can do in Microsoft word.)

You don’t usually want the bottom or foot of the bowl to be round. This means that the bottom of the bowl meats the horizontal at some angle. If the angle between the horizontal and the “bottom” is small, then imagine how the profile would look if you continued the curve through the center and up the other side. Have the foot high enough to lift this continued curve “off the table". If the intersection of the curve with the horizontal is fairly steep, the foot would have to be too thick. In this case you again imagine how the profile continues. You also decide how high you want the foot to be. The diameter of the foot is then determined by point at which the continued profile intersects the horizontal from the base of the foot. (Word does not have the resolution to show these things, but the book does.) A final word about feet. I have always made them as quite simple cylinders, or at best with a little outward curve. Raffan shows quite a few drawings where the foot has multiple-layers. The drawings look great, but all his photos show simple feet.

What about wall thickness? Let me start with a quote, “Achieving the right relationship between the inside and the outside profiles is at the heart of the bowl turners art.” Some the dos and don’ts: The side should be thicker at the rim and the bottom than in the middle. Sides that are thickest at the bottom and get thinner as toward the rim are not nearly as good. Sides that have equal thickness all the way are not good, particularly if they are thick. If the side is thicker at the rim, the bowl attractively “shadows” the inside. Note also that Raffan cares a lot about how the bowl feels as well as it appears when you are not holding it. Getting the two profiles correct helps the “feel” a lot.

Now the hardest thing of all – how do you learn to make the correct inside and outside profiles? Again a quote, “You will have to commit a terrible deed which my students dread. You will have to cut your bowl in half. This is a common practice among potters. I am sure it accounts, at least in part, for the large number of excellent ceramic bowls.”

So what is the bottom line?  There are three..  Read the book!  Remember 1.6.  And try making some bowls out of ordinary wood.  Bite the bullet and cut them in half to see how you are doing.