Although a bowl is just an open-topped container, there is more to a bowl than just its function. There are good bowls and there are bad bowls. An infinite variety of possible shapes, but far fewer really good ones. If you like a particular bowl and I don't, is one of us right and the other wrong, or is it just a matter of personal taste, with both views equally valid? Is it possible to be objective? A turner's work tends to evolve over time and I think this gives us clues. As well as exploring new ideas, they begin to see the faults of their early work.
There are no rigid rules about bowl design. Such rules as there are, are made to be broken. The turner can make any shape they like. But after thousands of years of bowl making, it's hard to come up with something completely new. Turners do manage to produce work that is original, or at least out of the ordinary. Originality is often a good thing, but isn't necessary, nor sufficient, to make a good bowl.
A bowl's design is independent of the wood it is made of, unless the bowl is shaped specifically to make the most of the wood features. Spectacular, highly figured wood is not enough, by itself, to make a good bowl. Colour, grain and surface treatment may be obvious attributes of a bowl, but its underlying shape must be sound.
A bowl made by a beginner is unlikely to be first rate. The challenge of turning a bit of tree into a functional bowl is enough, without too much thought about design. A bowl made by an inexperienced turner is usually easy to identify. It will often have a very wide and heavy base or foot; it will have straight, vertical walls; the walls will be thicker at the bottom; the inside bottom will be flat, so there is a sharp change of angle where the base blends into the walls; and the rim will be shapeless. The bowl may have been made using large expanding dovetail chuck jaws, leaving a deep recess where they were set into the wood. The flat bottom inside will be slightly undulating. The whole thing will show evidence of heavy sanding, and have a glossy finish that accentuates the torn grain beneath. Of course, some of these characteristics are related more to poor technique and limitations of the workshop equipment than to design decisions.
But time passes. The more bowls a turner makes, the more their eye and technique will develop, so that their later work is normally, hopefully, of a higher standard. A conscientious turner will constantly seek to improve, with each finished bowl better than the one before. They will have to make a lot of bad bowls before they can make a good one, but practice pays off. The time will come when they have developed their own style, and an eye for design.
In my opinion, following the guidelines below will make a good example of what might be called the 'standard' bowl design. A bowl that might be used for salad or fruit or nuts. They are not prescriptive, and no doubt there are lots of great bowls that break these 'rules'. There is any number of other types of bowl, for example wide rimmed bowls, natural edged bowls, thick-walled burr bowls, very thin-walled bowls, asymmetric bowls, sculpted bowls, etc, all of which are of course perfectly valid as good design.
- The design will not impede the intended function of the bowl, for example by making it unstable
- The shape will have curves that flow. There may be a slight change of direction, for example the walls may curve inwards, then out a little at the rim. There will not be a sharp transition between the walls and the floor of the bowl - the shape may be based on a cone, or be rounded, but not saucepan-shaped. The walls will not be straight unless by deliberate choice. There will be a slight curve to them.
- The walls will not be thicker toward the bottom. They may not have been calipered to the same thickness all the way down; often they may be thinner near the base.
- if there is external decoration, it will be near the top.
- The foot, or resting surface if there is no foot, will be quite small, perhaps about 2/5 of the diameter of the bowl. The bowl will be stable, depending on its intended function, but the small foot will give the bowl a visible 'lift'. (Some have a deliberately rounded bottom, which can look good.)
- The chuck recess or spigot, if present, will be unobtrusive. Signs of chucking may well have been removed by reverse turning, but I don't see this as essential.
- The rim will have some shape to it.
- Edges will be crisp, but not sharp. The bowl will feel good in the hand.
Such a bowl will be recognized as well designed by the majority of turners, and by craftspeople from other disciplines, such as potters. So some consensus is normally needed for a piece to be considered good. It may not be liked by everyone, but one that only its maker can love is either poorly designed or too far ahead of its time!