By making wooden bowls, the turner enters a world of creation that is thousands of years old. People have been using bowls for a long time and making them for the same time. The same design questions faced by the potter are also faced by the turner. One of them is how thin or thick the walls of the glass should be. It is necessary to answer a few questions to give some guidelines.
First, there is the intended use of the bowl. Is it going to be functional like a salad bowl or is it intended to be visual like a work of art? Generally, a functional bowl will be thicker to give stability and a sense of security. Artistic twists can be extremely thin to give a feeling of lightness and perhaps an ephemeral quality. On the other hand, a different artistic twist can be too dense and heavy to present other feelings and qualities to the viewer.
A third category may be a bowl made to impress and perhaps to impress turners in particular. In that case, it can be so thin as to allow light to pass through the oiled wood. To make one of these, the turners hang lights behind the swivel and thin the bowl to allow for even light distribution across the walls. It is a good test of skill and a learning experience.
Functional bowls should have walls that are thin enough to work with the intent of the part and thick enough to appear correct. As a general rule of thumb, an eighth of an inch thick for every inch of diameter seems fine with a little more for those six inches or less and a little less for bowls over sixteen inches. So an eight-inch bowl might be a quarter inch thick, while a six-inch bowl might be three-sixteenths and a sixteen-inch bowl three-eighths. Most of the time, the best thing to do is not worry so much about exact measurement as it is about appearance.
Consideration should also be given to where the bowl will be used. Restaurants may have certain criteria that they want to be followed, while a converted bowl for the outdoor deck on a summer night may have one-inch thick walls. The popcorn may fly, but the bowl will still be there.
Most of the time it is best to relax and prepare the bowl. If the lines look good and the bowl feels good, the design is likely good. Sometimes all the practice pays off and the bowl looks absolutely fabulous. The hunt makes all the twists a little more special.