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Zero3 L&H Cone 04-02 Glaze Variants

Zero3 L&H Cone 04-02 Glaze Variants


G2931L is a low expansion adjustment to the Zero3 K Glaze to make it fit Buffstone (without crazing). G2931H is a high expansion adjustment for fit high talc bodies (like L213, L212).


For stronger ware we recommend firing cone 04-03. Every cone higher you can fire will dramatically improve ware strength. All low fire bodies and glazes can easily tolerate firing higher. The chemistry of this recipe produces a more durable glass than commercial cone 06 glazes (they sacrifice hardness and durability to melt at a lower temperature).

To get the best defect-free surface please consider using a hold-rise-drop-hold firing schedule. For 04-03 consider using the PLLFDS schedule.

If you do not need strength and must fire lower (e.g. cone 06), then don't use this, use a commercial product.

Terrastone with Zero3 L glaze fired at cone 03.


We recommend decorating ware using underglazes, then overglazing with this and firing to cone 03. You can fire to 04 but ware will not be as strong and the glaze not melt as well.

If the specific gravity is around 1.43 and it is gelled enough it applies very evenly with little dripping. Ware needs to be absorbent. If your ware is thin it might be necessary to glaze the inside and outside in separate operations (with drying time in between).


As of June 2017 these are not yet available as a premixed products. But you can mix (and blend) them yourself. For our lab information on the recipes, how to mix and use them click here.

Thermal Expansion

Low fire glazes are much more difficult to match to the body, crazing and shivering are thus much more common than at higher temperatures. That is why we have three recipes: K, L and H. One of these will fit most bodies, if not they can be blended to fine tune fit. But there is another thing to consider if you intend to color or opacify: Adding zircon (for white) reduces thermal expansion and stains can move it up or down, so choose the appropriate base accordingly (or be prepared to blend them).

Do not use the Zero3 L glaze on Zero3 stoneware or on talc bodies (like Plainsman L215, L212, L213), it shivers. This is intended, it has the very low thermal expansion needed to fit non-talc, non-vitreous low fire bodies (like Plainsman Terrastone, Buffstone).


Buffstone and L215 with underglaze decoration and G2931 weigh-and-mix-yourself clear dipping glazes. But they are not the same. The G2931L glaze (left) has a lower thermal expansion (to slow crazing on Buffstone). The G2931K glaze fits L215 because the latter contains some talc (which raises its expansion). The L215 mug has survived a 300F-to-ice-water thermal shock without crazing or shivering. If you switch the glazes the Buffstone mug would craze it and the L215 would shiver it off in flakes.

Buffstone, L212 and L213. Each has its own clear glaze. G2931L, G2931K and G2931H.
L is low expansion (for zero-talc porous bodies like Buffstone). K is intermediate (for moderate-talc bodies like L215, Zero3 stoneware and porcelain). H is high-expansion (for higher-talc bodies like L212, L213).

Safety Data Sheet

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702 Wood Street, Medicine Hat, Alberta T1A 1E9
Phone: 403-527-8535 FAX:403-527-7508