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The care and feeding of your glassblowing furnace

Well, this Fall has been a series of furnace issues! Owning and managing a glassblowing studio is not for the faint of heart, the risk-averse, or those on a tight budget! Ouch!  

Last year we had to rewire our furnace with a high-temperature wire that cost a pretty penny. This year we emptied the furnace of glass; everything looked okay! We charged the furnace only to notice that the sill was half gone. We were working all day making pumpkins and gathering from the other side of the sill. All the time we were thinking about how we were going to have to install a new sill in the hot furnace!

The next day we came in, and the furnace had shut off. It should have been at our working temp of 2050 degrees; instead, it was at about 1200 degrees! Boy was that a bummer! We checked everything we could and called our electrician. He came out and did some troubleshooting. We all decided it was the controller. Then we put in an order and had to hurry up and wait for it to be built and arrive.

Meanwhile, the furnace was slowly coming down to ambient temperature. We thought the old sill might have been broken during charging, but then when we took it out we saw that it had just been eaten up by glass! It’s always good to keep extra parts around for emergencies. We had an extra sill, so swapping it out wasn’t a problem. Now, to continue the wait.

After a lot of drama, the new controller arrived. Of course, traffic was horrendous that day, and our electrician was late. They installed the controller, but nothing worked! After several hours of trying to figure it all out, they thought they had found a workaround. The furnace was starting to come on. They left, and Patrick watched the furnace for several hours. At this time the furnace temperature was at ambient conditions. You must bring the furnace up slowly, especially when your crucible (pot) is full of glass in hopes that everything will be okay. So he programmed it for 11 degrees/hour. By midnight he realized it wasn’t working. He decided to check all the programing but with no success.

We huddled the next day trying to figure it out. We had met an excellent customer who was an engineering manager with a temperature control firm. He had said we could call and maybe he could help! I gave him a call, and he was a godsend! That afternoon he came out after work. My electrician’s son came too to gather info. Our new friend Richard was able to get the new controller up and running, but then troubleshooter and found out that we had a faulty thermocouple!  

There are two thermocouples in the furnace, one which signals to the controller and the other one to the redundant high-temperature limit. The one that is no longer working goes to the upper-temperature limit; however, the second one looks just as bad. We could opt to hotwire the high temp limit to the one still working, but that might mean that we would come up to temp and then break down again. So we wait! We have ordered three thermocouples, and it will take 2-3 weeks to build them. Then it will take about a week for the furnace to come up. Hopefully, the pot won’t crack as we slowly raise the temperature.

Glassblowers live and die by their furnace! Send your positive energy our way! Lift us up to the glass gods and keep your fingers crossed! We hope to be back to blowing mid-October!

3 Comments

  1. Marilyn Taggi Cisar on September 20, 2019 at 2:57 pm

    So sorry to hear about all the problems with the furnace and controllers. It never rains, but pours. Literally and figuratively. I was just about to set a date for our annual MIT pumpkin event !

    • Sally Moore on September 20, 2019 at 4:22 pm

      Thanks Marilyn! I know we can get things up and going for your event! Looking forward to having the MIT folks out to the studio again!

  2. Greg Fleischaker on October 14, 2019 at 3:52 pm

    What a horrible feeling, so glad you figured it out and are now back up and running, I certainly missed renting your studio while you were busy with repairs!

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