by Potterings
If you could open a kiln during a glaze kiln firing (never do this!), you would find glazes glowing like molten galaxies. You may have guessed that glaze firing is magic, science, and happiness-inducing suspense all rolled into one. It’s a thrilling moment to share a finished and glazed piece of pottery with new and beginning students.
But what actually happens when glaze meets fire inside an electric kiln?
From Powder to Glass: The Transformation
When you first glaze your pottery, the surface looks chalky and fragile, because it is. Glaze at this stage is essentially a powdered blend of minerals suspended on the surface of your piece. Once the kiln begins heating, a remarkable series of transformations takes place:
- Water evaporates (bye-bye damp pots!)
- Organic materials burn out (you might smell this in the early stages)
- Silica begins softening and fluxes start doing their job, melting and melting and melting…
- The surface becomes liquid glass (yes, that glossy pool of color is literally molten glass!)
- Oxides react, melt, move, float, separate, speckle, or blend to create effects impossible to fully capture any other way
Electric firings, like the ones we rely on at Potterings, are oxidation firings, meaning plenty of oxygen is present. This affects color results, especially with minerals like iron (creamy browns, honey tones), copper (greens rather than reds), and cobalt (those dreamy stable blues).
What Makes Glaze So Unpredictably Gorgeous?
Once molten, glazes are alive, well, not literally, but they flow, shift, break over texture, and can mingle at the edges like watercolor on wet paper.
Common effects you might see in the kiln include:
✨ Breaking – when the glaze gets thinner on the edges or texture, revealing the clay or underlayer
✨ Pooling – thick glossy areas where glaze gathers in recesses
✨ Crystals forming – slow cooling can produce visible crystal blooms
✨ Speckles – certain glaze recipes include materials that burst into tiny freckles of color
✨ Interactions – layered glazes sometimes react dramatically (sometimes beautifully… sometimes surprisingly!)
This is why no two pots are ever alike, and why we adore handbuilding so much.
Cone 5: Potterings’ Sweet Spot
At Potterings, we fire to Cone 5 (around 2167°F / 1186°C), the goldilocks zone of mid-range ceramics.
Why Cone 5?
Hot enough for durable, functional ware
Cool enough for vibrant glaze colors and controlled movement
Perfect balance of surface durability and artistic effects
Cone 5 glazes melt fully into glass but don’t become overly runny, giving us that ideal balance, glossy but not drippy, bold but not unstable, striking but sturdy enough for daily use. Our studio glazes are tested for reliable results at Cone 5, so beginners can explore with confidence while more advanced makers can layer and experiment.
The Joy of the Unknown (a.k.a. kiln Christmas)
Even with all the science, there will always be an element of surprise; that’s the beauty of glaze. The kiln takes your ideas, stirs them together, and adds its own spark.
So whether you’re:
- making your first handbuilding piece in a beginning handbuilding workshop, or
- trying an open format class during Open Studio on Wednesdays from 6–8 pm,
…remember: the kiln is your collaborator, not just your tool.
Ready to Play With Fire (Figuratively)?
We love guiding makers through every step of the process, from shaping clay to opening kilns with wide eyes. Join us in the studio, experiment with glazes, and experience the thrill of transforming earth into art.