Thursday, September 23, 2010

Replacing the Crucible

Summertime is way too hot to blow glass. So usually glass blowers sit back in the air conditioning with our feet up, sipping cold beverages. Okay, that was really a joke.

When the furnace is down our minds turn to studio maintenance. It's certainly not my favorite thing to do, but it's necessary. I have to admit with all the help I had pulling the pot this year it was actually fun (I really didn't do any of the work). John Martin, Harrison Harper, Elijah Leed and Nate Halsey all helped make it happen with lightening speed. Thanks guys!!

Why does the pot (or crucible) have to be removed from the furnace? The crucible is made of a high temperature ceramic, made to withstand temperatures in excess of 2400 degrees Fahrenheit. The glass is corrosive to the crucible so over time little pits develop. If left too long these pits could actually grow large enough to be a hole all the way through the pot - and the molten glass would run out into the bottom of the furnace. And that means unplanned down time and LOTS more equipment maintenance.

Usually I take the furnace apart and proactively replace the crucible once a year. Prior to doing that I can melt colored glass. Residue of color added to the crucible will tint future glass, so if you melt clear glass you really can only melt clear glass... until you are ready to replace the pot.
It's quite an exciting time! This year we melted turquoise, cobalt and black glass. I will admit I let a little glass drip over the side of the pot thinking that might look good. And it is quite beautiful.

Once the furnace was all put back together we started "firing up". The process of heating up to 2300 degrees and melting a pot of glass takes about a week, since we don't want to crack the new crucible. Now we are back blowing glass - the glass is hot and we're sweaty!

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