About Bisque and Raku Firing
All of my pieces go through two firings. The first, known as 'bisque firing,' is done when the piece is in its 'bone dry' stage (the most fragile state) and fired over 8-10 hours, peaking at a thousand degrees Celsius. In the ceramics world, this is considered a low-temperature firing, specifically at cone 06—more on that later. In this stage, the pieces are not glazed yet, so they can touch one another inside the kiln and be stacked, making this first firing very cost-efficient. We fire many pots at a low temperature for not that long. When clay fires at a low temperature, it won't have its full strength potential, but it will be solid yet quite porous, which is essential for the piece to absorb glazes. At this point, the piece is ready for its second firing, in my case, Raku.
Once all pieces are glazed, I carefully place them inside the kiln, ensuring there is no glaze on the bottom of the piece or excess that will run off. Each piece needs its own space in the kiln at this point. If they touch, they will merge. Full kilns, with more mass to heat inside, fire better, so we make use of all the space. Pyrometric cones are carefully placed inside the kiln near a slot opening at a specific spot to take a peek while firing. These cones are made of a ceramic material with different ratios of added flux, a melting agent, precisely to determine the temperature inside the kiln. Once they start melting, you know the kiln has reached the desired temperature. I know what you're thinking! This is crazy, how often are you checking on that cone? I place three different types of cones, so I know when I have passed certain temperatures, and we also place a digital pyrometer reader on the side, although those are not very precise.
Here comes the fun part. Each piece has a designated lidded metal can to be placed inside to enter into a reduction atmosphere. Once the kiln has reached 1000 degrees Celsius, the pieces are pulled out of the kiln, glowing red hot with long tongues, and placed inside their corresponding metal can with a combustible inside. It immediately catches on fire, and we close the lid tight. Once the fire inside the metal can has burned up all the oxygen, it creates a reduction atmosphere inside, causing the glazes to chemically react. Isn't that beautiful?
What I like most about Raku is the process itself. It's very fun to watch. Typically, I will host an event for it. Would you be interested in joining?
