Today I am sharing a failure. Let me just say that it is so much more fun to share successes! But I do learn a lot from the failures. And since I promised to share the journey, this is part of it.
A few months ago I made custom handkerchief vase for someone. She loved it. Unfortunately the cat jumped up on the table where the vase was sitting and knocked it over. So she asked me to make another one for her.
I will start by saying that whenever I put the glass for a handkerchief vase in the kiln, I always set the temperature alarm to go off when the kiln reaches the process temperature. The process temperature is when the glass takes its shape. I program the kiln to hold at the process temperature for 10 minutes. But in reality, when the kiln reaches the temperature I watch it very closely. The trick is to stop the heating when the glass has taken on the shape you want. Sometimes it takes just 2 or 3 minutes. Other times it has taken 15 or 20. It all depends on the type of glass, and how thick it is.
I put the glass for the replacement vase in the kiln. I set the alarm and went about doing some other things. Several hours later I began to wonder why I hadn’t heard the alarm yet. I went to check on the kiln and discovered that I had set the alarm for a higher temperature than the process temperature. The alarm never went off. I had a dyslexic moment when I punched in the numbers. This meant that I had totally missed the process temperature! The kiln was already in the cool down phase of the process. The glass was at the process temperature for 10 minutes and I had no ideas what it would look like.
When the kiln finally reached room temperature and I could open the kiln, I was not happy! Ten minutes was way too long. The glass had draped too tightly against the form. As I removed the form a piece broke off. Not only was the shape not what I wanted, but the color had changed as well. Some glass changes color when heated. This is referred to as “striking” and the results vary by temperature and how long the glass is heatworked. The glass that I put into the kiln was a dark burnt orange color that was transparent. What came out was a brighter, lighter orange that was opaque!
So the lesson was a very basic one. Check the numbers very carefully!