When blowing glass, temperature is one of the most important measures we regulate.
Our glass furnace runs for 24 hours a day, seven days a week. To be frank, our furnace is a work horse that never gets a break. It runs at temperatures between 2,000°C and 2,200°C (3992 °F) in order to melt down the post-industrial, recycled glass we use for the base of most of our products.
It all starts when the clear glass chips are put in the back of the furnace to be “charged,” which is the initial heating and melting process. As it liquifies, any dust or debris in the glass burns away. Once fully melted, the glass flows into a second chamber where it pools and becomes molten glass that’s ready for use.
That molten glass is between 1,100 C and 1,800 C when glassblowers gather it from the furnace and begin working on a piece. This allows the glass to be pliable enough to take on the desired form.
A glassblower will often reheat their piece by placing it in a “glory hole” because it cools quite quickly. This is also how they melt the coloured glass frit into the piece to create our beautiful patterns.
Upon completion the glass piece is generally about 500 C, which is too hot to cool in the natural environment. If left to cool naturally, the inner glass will cool at a different rate than the outside of the glass. This means the glass could crack or develop weak spots.
In order to protect the integrity of the glass piece, we put them through the annealing process. This means the glass will be cooled evenly inside and out, and reduce the chance of cracks or weak spots.
Most of our pieces go through the lehr to complete this annealing process. It is a conveyor belt that slowly cools the glass until it reaches ambient temperatures. This generally takes about 3 hours.
We also have several annealing ovens that are used to cool larger items that take more time to cool. At Kitras we often program this to happen overnight (8 to 10 hours).
Once the glass piece is through the annealing process, it’s inspected, packaged and ready for you to enjoy!