Notes on crystalline glazes

Crystalline glaze recipes contain zinc oxide, silica, and fluxes.

crystals of zinc silicate (Zn2SiO4) are formed.

A window of approx. 72 C (130 F) exists in which to grow crystals.

Crystalline glaze is fired higher than the melting temp. of the glaze, at least 222 C (400 F) hotter. Once this point is reached, the temp. should be quickly reduced to the temp. range for crystal formation, then kept within this range for a predetermined time.

Sequence to promoting crystal formation:

  1. Getting to max. temp. as quickly as possible.
  2. Rapidly cooling to the crystal growing range.
  3. Extendeds oaking, or slowly dropping and raising the temp. within the crystal growing range during the crystal growth period.
  4. Shutting the kiln off and cooling naturally.

^04 Cenote

https://glazy.org/recipes/89827

Cenote on Sedona Red ^05-02 clay body.

Blue-violet overall to violet where the red clay body shows through, ultramarine blue with greenish-gold mottling where thickest. Crazed where very thick. Significant movement.
4 coats brushed on interior of the test bowl. 2 coats on rim. Fired to a hot ^04. Kiln schedule posted.
Generic emerald green on ^5-10 buff clay body. Light yellow-green to light green to aqua, depending on thickness, on ^05-03 talc/ballclay body. Significant movement on all three clay bodies, with the most movement on the buff and red earthenware clay bodies. Crazed where thick on Sedona Red and buff clays, no crazing on the white talc/ballclay body.
4 coats, brushed, on the two test tiles. Four coats, brushed, on the little test bowl interior, 2 coats on rim. Fired to a hot ^04.