I recently bought a ceramic ruffled plate mold at a sale for $6. What a deal! However, when I used the mold the first time, the resulting plate did not rest flat on the table, and instead rocked driving me crazy. I realize that not all tables and countertops are completely flat either, but this was enough of a rock that it was clearly an issue.
At first to resolve the issue, I put the plate back into the kiln and refired to only 1050 degrees F rather than 1200 degrees F but the result was less of a ruffle on the plate. Time to figure out how to resolve the real issue.
My husband works with metal which is very exact and helped me figure out how to solve the problem. Here are the steps I used.
1. Figure out which diagonal is rocking and mark that both on the glass and the mold. It is really important to keep track of this diagonal as you work through the issue. The glass is rocking on this diagonal because one of the corners on the mold is not low enough for the glass to slump into.
2. It doesn’t matter which of the two corners you work on that diagonal, as long as it is one on the problem diagonal.
3. Use sandpaper (I used 220 grit) to sand down the ceramic mold in that corner where the glass needs to slump lower. The goal is to sand it far enough that the two corners can slump equally.
4. So how can you tell if you have sanded the mold far enough? Take a small ball of clay and put it on the mold where you are sanding at the low point.
5. Place the glass plate onto the mold and flattened the plate into the mold squishing the ball of clay.
6. When you lift the plate, turn it over and see how thin or thick the clay is. This thickness is how much farther you need to sand to get the mold even. You can test this by taking the glass with the clay still attached and placing it on a known flat surface to see if it lays flat. My plate no longer rocked with the clay so I knew this is how much farther I needed to sand.
7. Sand some more and repeat the test until you get to where the clay ball thickness was miniscule. Ultimately I learned to sand this slightly more than I thought I needed as I am guessing re-kiln washing ended up adding slightly to what I had just sanded.
8. I then kiln washed the mold and re-slumped the plate.
Ultimately I did this test and re-firing twice to get it right but it does work. And remember that many surfaces which we think are flat are indeed not flat. My husband owns something called a Surface Plate which is designed to be flat for just such testing.
For me this was worth the effort as the rocking really bothered me. I did have to laugh though as I later realized that many of my store-bought regular dining plates did not sit flat on the table either due to either typical manufacturing inconsistencies or tables and counters not always being flat.
I loved learning how to resolve the issue with the mold and make my glass plates better.