Gorgeous Iridescent & Metallic Effects
Mayco Raku glazes are designed to develop beautiful metallic lusters and crackle patterns when fired according to raku firing processes. There are several methods and many nuances to raku firing - for our purposes here we define raku firing broadly as the processes of firing an earthenware body and glaze in a kiln, removing the ware from the kiln after it has reached proper temperature, placing it in a container of combustible material and enclosing the container to reduce the oxygen in the container.
The following application recommendations are based upon the original product development intent and use for the product. Information on alternative application methods is listed in the section "Usage Variations and FAQ's".
- Shake for 5-6 seconds before use. Stir well.
- Apply 2 coats to cone 04 bisque (1940°F, 1060°C).
- Do not glaze bottom of ware.
- Allow to dry thoroughly.
- Fire to cone 06 (1850°F, 1010°C) and hold for 5 minutes.
- Reduce in your choice of combustible materials.
- Thinner coats tend to produce greater metallic effects. If you are not getting the desired metallic results you can adjust your glaze application.
- Use of a thermal shock-resistant raku clay body will help reduce the incidence of cracking.
- Actual fired results will vary according to choice of clay body, glaze application thickness, glaze fire temperature, combustible materials, reduction process, kiln, etc.
- If using an electric kiln make sure power is off before removing ware with metal tongs.
- Minimizing the distance between the kiln and the reduction container can improve the development of metallic colors.
- After ware has completely cooled use water and a scouring pad to clean; cleaning will improve the luster and colors in the fired finish.
Usage Variations and FAQs
Q:Your label states that Raku glazes are "Food Safe", yet you also include the statement "May not be suitable for food surfaces due to surface characteristics"?
A: 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.
Notes on Safety
Proper safety processes and personal protective equipment are very important when doing Raku as you are exposed to high heat, flames and smoke. Always wear fire protective clothing, fireproof gloves and protective eyewear. Do not open or insert tongs into an electric kiln without shutting off. Reduction process should take place outside of building due to flames and smoke. Do not spray apply glazes without a NIOSH approved respirator and other personal protective equipment. Non Toxic and Non Hazardous when used according to manufacturer’s directions. Not Recommended for Food Surfaces."
Mayco Raku Glazes will display a variety of iridescent, metallic and/or crackled fired surfaces. (Chip sample on label was fired to temperature, at the maximum ramp rate, and immediately reduced in a lidded container densely packed with a mixture of newspaper and straw).
Raku glazes are not recommended for dinnerware due to the durability of the fired glaze. Some glazes, regardless of surface texture or porosity of underlying clay body, will be designated as not suitable for dinnerware as the fired glaze surface is not durable and can be impacted by contact with food or liquids. While it may not be harmful, it is certainly not desirable. Recommended for ornamental use only.