Crackle Gloss Glazes

Crackle glazes, while visually stunning are technically "bad fitting" glazes because they do not expand and contract in harmony with the clay to which they are applied. Most glaze is intended to seal the clay to make it water-tight. When a crackle glaze is used, that seal is "cracked" and the ware can leak. This difficulty can sometimes be overcome by using a crackle on the outside only, and a non-crackle on the inside. This usually only works with comparatively thick clay ware. On thin ware, this cracking can pass through the thin wall and crackle the non-crackle glaze, and in extreme cases, cause very thin walled ware to crack. Obviously, crackle glazes are not dinnerware safe, or good for vases which are to hold water. Use these glazes for DECORATIVE WARE ONLY. A fairly thick application is needed to insure good crackling. The crackling effect starts when the glaze hardens and is nearing the cooling end of the firing cycle, and continues after the ware has been removed from the kiln and can continue for a week or more. To get the full crackle effect, do not apply stain until the glaze has stopped crackling.
Staining crackle glaze - In most crackle glazes, particularly opaques, the cracks are not readily apparent until they are stained. The stain may be of any colorant such as iron oxide, umber, sienna, colored/india ink etc., mixed with water and brushed or rubbed over the glaze. After the stain is applied, it is wiped off the surface but will remain in the cracks and visually delineate the crackle pattern.