Low-Fire vs. High-Fire Glazes: What's the Difference?

Not all ceramic glazes fire the same way — and mixing up a low-fire glaze with a high-fire one is one of the most common (and messiest) mistakes a beginner can make. Here's what the difference actually means, and why it matters.

It's about temperature, and matching your clay body

Glazes are formulated to melt and mature at a specific kiln temperature, measured in cones. Low-fire glazes mature around Cone 06–04, roughly 1830–1945°F, and are the standard match for earthenware bisque. High-fire (stoneware) glazes mature much hotter, typically Cone 5–10, around 2160–2345°F, and are made for stoneware or porcelain clay bodies that vitrify — become dense and non-porous — at those higher temperatures.

The clay and the glaze need to be fired to a compatible temperature together. A stoneware piece only fired to Cone 06 won't reach the temperature its clay needs to vitrify, and a low-fire glaze taken all the way to Cone 6 will often over-melt, run, and potentially damage kiln shelves.

How to tell which one you have

The cone range should always be listed on the glaze itself — check the label or product listing before you buy or fire anything. If you're working with a piece of bisqueware and you're not sure what clay body it is, that information is usually listed on the product page too (ours always lists the clay body and cone range together).

Why this matters more than it seems

Firing a mismatch isn't just a cosmetic risk. An over-fired low-fire glaze can run off the piece entirely and fuse it to the kiln shelf — a genuinely frustrating (and expensive) mistake. Under-firing a high-fire glaze, on the other hand, usually just leaves it dry, rough, and dull, since it never reached the temperature it needed to melt properly.

The safest habit: always check the cone range on both your clay and your glaze before you fire, and when in doubt, fire a small test tile first.

Explore both

We carry both ranges — browse our Stoneware Glaze collection for high-fire work, or the full Glaze collection to see everything, low-fire included.