A small bowl may seem okay when you look down at it from above, but there could be issues with its wall thickness. Perhaps one side is much thinner and lighter than the other. Or the rim may not look even until you realize the clay is becoming firm and hard to fix. When making handmade decorative plates and bowls, even thickness doesn’t necessarily mean you have to perfect your piece, it’s just another factor that can help your clay to maintain the best form possible when smoothing, stamping, carving, moving, or allowing it to dry.
It is common for pieces to develop uneven wall thicknesses if there was uneven pressure applied during the forming process. If you are pinching a small bowl to create a form, chances are you are not squeezing with even pressure because one hand is likely your dominant hand. If you are working from a slab of clay to make a small plate or platter, your rolling pin may not have rolled with an even weight or pressure and one side of the clay may be thicker than the other. This may be hard to see at first, but it is something that will determine how a piece sits on your workboard or how the rim feels when smoothing it to a particular thickness. It can also affect the surface once you stamp, carve, or underglaze your piece.
One of the most common issues with uneven thickness is when the base is a lot thicker than the rest of the walls. Because the thicker base has more clay to dry, the rim of the bowl will dry sooner. This is not ideal because it can affect the balance of the piece and may cause it to curl or crack during drying or result in a fragile rim. If you have an opposite problem, where the base is thinner than the walls, it may bend if you lift the piece from its bottom or it will not be strong enough to be carved into or have a texture applied to it later. While you are not trying to make your base exactly match the rest of the walls, you don’t want any drastic difference between the clay at the base compared to the rim or other areas of the piece either.
Try checking the thickness of clay in your piece before decorating. Gently hold the piece up and place both hands on each side so you feel the thickness of the walls with just a little pressure. Move slowly and carefully over the piece instead of holding it too tightly to feel if your clay is even. If you’re checking a small bowl, look at the rim from the side and see if it rises evenly on its base. If it’s a slab plate or platter, run your fingers over the edges and middle to see if there are any dips or thinner areas of clay. Use a metal or wooden rib tool to firm up the clay so that you have an even surface on the inside and outside of your piece, but remember that you don’t want to push the tool too aggressively or you might make the piece thinner in one section than another.
As an exercise, make two smaller pinch bowls from approximately the same amounts of clay. Form one as you normally would and make a note of what you feel like when it is finished. For the second, check it with your hands every minute to see how the base and sides are changing in thickness and feel. Use a damp sponge to add moisture to the surface, but be careful not to add too much water to your clay as you work. Once you’ve finished both pieces, lay them on a flat surface and see which one wobbles or which one has a thinner edge. While this exercise may take you slightly longer to make your form, you’re more likely to notice and adjust what hand you’re using with more force as well as other ways you can improve your pinch bowl technique.
Your piece will be easier to decorate when the clay body has an even thickness and isn’t collapsing on the surface, and carving will be less risky. With more even walls, you will have a better surface to make slip marks, painted designs, or stamped into it. It is something to keep in mind when you’re trying to stamp or paint onto a surface that is not going to be flat. Even if you are working on a simpler form like a spoon rest, you should take the time to see if there is an uneven surface before trying to add any decoration. When you’re ready, add a little underglaze or slip to finish your small dish.
When you’ve finished creating a piece, think about where the clay is having the most work being done by you. The rim may feel too thick to carry the shape and may need to be thinner or lower, or you can leave it if it’s working well. If the base feels heavy, you can try a lighter touch to make the clay less heavy. If any one section of the wall feels too thin or is bending when you touch it, stop before you decorate it. Try to see if your wall thickness is too varied early in the process so you don’t have to add too much to it to make the piece feel strong enough.