10th
Pop Quiz Answers: Problems Throwing Pots
I posted a dozen or so questions for you wheelthrowers to test your problem-solving chops when it comes to making pots.
Here are the answers I had in mind. Do they jibe with what you know? Did I miss anything helpful?
ANSWERS: Common Problems in Throwing Pots
1. Air bubbles come from insufficient wedging, improper wedging or trapping air when you attach your ball of clay on the wheel.
2. Either you opened the clay off-center or the wall was torqued off-center during pulling, usually from the clay being dry and grabbing your fingers.
3. Either your lip was too thin to handle being opened up that far, or the clay is short (not optimally plastic). Any session you find only short clay to work with, it’s best to revise your plans to work on projects that demand less of the clay. (Avoid very tall shapes, very thin shapes, shapes that cantilever out far over the base, and handle-pulling where possible.)
4. You are overworking the clay and/or adding too much water. Try to get your walls extended in three pulls. Rib down your walls between pulls. Finish the lip before you finish thinning out your walls.
5. The step inside your bowl comes from unintentionally applying greater pressure when your fingers clear the floor of the bowl. Your fingers align at this point in the pull the same way they do when you’re throwing a cylinder and it becomes easy to thin the wall too much at this point, creating the step. Use greater pressure when shaping the floor of the bowl and then ease up pressure from your inside hand as you make the transition from throwing the floor to throwing the wall of the bowl.
6. There is hidden weight because the inside shape does not match the outside. Analyze how the inside would look to match the outside silhouette you like, and then throw that shape with the next bowl you make.
7. The foot of your bowl was not fully on center when you attached it to the wheelhead to trim. Note that you can trim a centered foot ring on a pot whose foot and lip are not on center with each other. Alternately, your pot dried unevenly, and the stiffer side resists the trimming tool, making for an asymmetrical foot.
8. The lip crack was caused during the trimming process. The lip was too dry to bear the pressure of trimming.
9. It is a moisture crack caused either by leaving water standing in the floor of your pot while you’re throwing, or by not compressing the floor enough before starting your pulls. (Both lead to too much water between the clay particles, which leaves the floor prone to S-cracks.)
10. This is a moisture disparity issue. Either your mug was too dry to take a handle when you attached it, or you forgot to score and slip, or you forgot to let the mug rest under plastic after you attached the handle.
11. You want to center your dome of clay as narrowly as possible while still being easy to open. (Typically the taller the dome, the harder to open on center.) Then after opening and forming the floor, use both hands at the base of the clay to constrict the outside diameter to approximately the finished width you’re aiming for.
12. As soon as your pot is dry enough to handle (on the soft side of leather hard) flip it over and let it finish drying upside down. The trapped air ensures even drying throughout the pot.
13. That pot is much too dry to trim. Rather than give yourself and you neighbors a foundation for silicosis, consider tossing it in the reclaim and throwing another, or finish it with a surform rasp.
14. That pot is still too wet. Let it dry more, or trim very carefully and very slowly. (Speed kills.)
