Usage Variations & FAQs
The "crackle pattern" in the glaze is actually a firing defect called "crazing." Simply put, crazing is occurs when the glaze shrinks more than the body. The tension of the glaze on the body causes the glaze to crack.
In the case of Classic Crackles™ it is our intent to develop a glaze that will not fit an earthenware body. While we design and test for a common cone 06 earthenware body we know body composition can vary. If you having diificulty obatined a crackle pattern one potential issue may be that the glaze "fits" the body too well.
Some things you can try to instigate cracking:
- As the kiln cools enough to open, remove the ware and expose it to cooler air. The thermal shock may induce cracking.
- Use a spritz bottle to lightly spray water onto a ware piece as this may also induce cracking.
- Try a different clay body or source of bisque.
- Always test to find the best body/glaze combination that gives you ideal results before engaging in mass production.
Food Safety is determined by standards established by the Food and Drug Administration (FDA). ASTM method C-738 and C-927-80 are "leach tests"; the tests involve measuring the chemical composition of an acidic food before exposure to a glazed surface and the chemical composition after a several days. If the levels of glaze materials found in the food are below the established limits, the glaze can be marketed as "Food Safe."
Glazes that create dimensional surfaces also create crevices and nooks that can trap food - even after washing. This food can develop bacterial growth and cause health issues. Our policy is to discourage the use of textural glazes on ware that is intended for food usage even though the glaze has met all food safety criteria.
Yes, you can do both. Classic Crackles™ are transparent and easily allow designs on the bisque surface to appear through. Glazes such as Stroke & Coat® and Foundations work very well for design work under Classic Crackles™. Use only 1-2 coats of the glaze under to create the design; too much color may prevent the crackle from developing properly. Apply three coats of the crackle glaze and fire to shelf cone 06.
Design work on top of Classic Crackles™ will remain intact after firing as the crackle glaze does not move.
Overglazes, such as Gold and Mother of Pearl, can be used on Classic Crackles™as can low fire decals.
You can use non fired products or fired products to highlight the crackle pattern.
If you plan to highlight the crackle: handle the glazed ware with gloves or a clean rag to avoid getting dirt in the cracks. Oils from your hand can also prevent the antiquing color from filling in the cracks. While black inks and glaze are commonly chosen, you can chose any color to accent the cracks.
Fired products: you can use any glaze to fill in the cracks. Wipe glaze into the cracks with a clean rag and refire to cone 06.
Non fired products: use acrylics, mineral spirit stains or India ink to stain the cracks. Wipe onto the piece with a clean rag until the cracks are adequately filled in.
Crackle glazes place stress on the ware during firing. To prevent containers, such as vases, from splitting or cracking apart make sure a compatible (not stiff) non-toxic glaze is used to coat the inside of the vase. Compatible Mayco glazes include Foundations, NT-Clear. Allow ample room between pieces in the kiln for air circulation.