Answered By: Beth Hylen Last Updated: Oct 27, 2016 Views: 10
From the Studio:
The melting furnace in the hot glass show contains about 250 lbs. of colorless glass. Color can be added by using frit to coat the gob of glass on the end of the blowpipe. The furnace is operated 24/7 and
is maintained during off hours so that 250 lbs. is a constant the level goes down as used, and the furnace is refilled during off hours with new glass and cullet, usually every few days depending on usage. The furnaces are not shut off because the molten glass would contract during its cooling and would pull the inside of the furnace inward-breaking apart the refractory and dramatically shortening its life, and contributing to very poor glass quality upon re-warming. The furnace could be emptied first, and then successfully cooled. The furnace takes 3-4 days to warm up and the same to cool down, so it is unrealistic to do it frequently. Furnaces are fueled by either natural gas, electricity or propane. The indoor hot glass show furnaces are electric.
Questions: 1) Who services the furnaces and when, both in the hot glass show and in the studio? Furnaces have their weekly and monthly maintenance done by in house technicians here at The Museum both at the HGS and Studio. It happens early morning or in the evenings, depending on the nature of the maintenance. That being said, furnaces can run for long periods with very little need other than refilling the glass.
2) How often do the furnaces require maintenance/repair? Maintenance every month or several months, repairs usually as soon as something goes wrong to avoid affecting the furnace’s ability to stay hot and produce good quality glass.
3) In the studio furnaces, if the pot of molten glass contains colored glass, what happens to the left over glass after the objects using that color are made? Is colorless glass then introduced to the furnace? The reason I asked this is that I once saw one of the studio furnaces labeled blue.
We only melt colored glass in a separate furnace, because you are correct – the color contaminates the clear. When we are done with one color, we often “wash” the residue color out with clear glass (and subsequently ladle out the wash glass) or transition to another color that can assimilate the residue without adversely affecting the new melt.
4) Is the molten glass in the furnaces in a pot? Will the ovens in fact implode if molten glass is allowed to cool? Not all furnaces melt in pots, but many still do. The other major style of furnace is a “tank” furnace (or large rectangular chamber). The pots do crack if cooled with significant amounts of glass in them. They won't implode, but what happens is the glass cools and contracts, but the ceramic cools and contracts more. Cracks can easily form from the stress involved.