Crystalline Slow Cool glazes are a special type of ceramic glaze designed to create visible crystal formations in the glaze surface by controlling how the kiln cools after firing.
What They Do
Unlike regular glazes that just melt and harden into a glassy surface, crystalline glazes are formulated so that crystals can grow in the glaze as it cools. These crystals produce unique visual effects — such as starbursts, petals, or organic crystalline patterns — that are impossible to achieve with standard glazes.
The colours, size, and number of crystals vary depending on the glaze chemistry, application thickness, and the firing schedule.
Why Slow Cool Matters
Crystals don’t form immediately — they need time and the right temperature range during the cooling phase of firing. Slow cooling:
Extends the temperature window where the glaze is still fluid enough for crystals to form and grow.
Encourages larger, more dramatic crystal growth compared with rapid cooling, which “freezes” the glaze too quickly for crystals to develop.
With Coyote Crystalline Slow Cool glazes, the chemistry is tuned so that these effects can be achieved without needing a totally separate firing cycle — they work within a controlled slow-cool schedule that’s compatible with other glazes.
How They’re Used (Studio & Class Context)
Apply these glazes to bisque ware like other mid-fire glazes.
The kiln must be programmed (or manually controlled) to cool slowly through a defined range, rather than shutting off and letting the kiln drop temperature quickly.
Results are somewhat unpredictable — even within the same glaze — so each piece is unique.