To understand “Raku Glaze” it is important to have a general understanding of the Raku Process itself. On first introduction to the process, when a person views the red hot ceramic pieces being removed from the kiln, they generally comment on the extreme HEAT involved. Yes, they’re hot, but not by comparison to the firing process used when one makes dinner ware: mugs, bowls, plates, etc. which is considered “high fire” (around 2350 degrees). By contrast, Raku firing is a “low fire” process (from 1650-1850 degrees).
IMPORTANT: Raku ware is for DECORATIVE use and is not food safe. Because it is a low fire process, the clay itself remains porous and, in addition, some of the ingredients in the glazes should not be used with foods.
Technically speaking, ANY “low fire” glaze (a glaze formulated to mature at lower temperatures) can be used in the raku process! Will all low-fire glazes be successful and produce the results the artist may be seeking? Likely not, but there is MUCH room for experimentation by the artist who enjoys working with the serendipity of the raku process.
Glazes can be applied to ceramic ware in a number of ways….they can be: poured, painted, splashed/spattered, sponged, sprayed, dribbled, or any other way a creative artist might think of! As for me, I prefer pouring interior glazes and spraying exterior glazes. I also spatter/splash/drip contrasting raku glazes on certain pieces for visual texture.
Various ready made Raku Glazes can be purchased from a variety of sources, but many artists – myself included – prefer to mix their own. There are many online sources for glaze ‘recipes’ and one of the best single resources I am familiar with is Gary R. Ferguson’s Raku Glazes – The Ultimate Collection available through Amazon.com.
I have a palette of glazes that I have worked with for years and still do experimentation with new formulas as time allows.
My main colorants for my basic palette are copper and cobalt carbonate, seen here in raw state. These colorants, along with the Raku Firing Process, are what produce the metallic and iridescent colors you see in my work.