Joss Research: Ceramics: Glazes: “Rumoku”


Adding Rutile to High-Iron Glazes

(2005 March 15)

This little covered jar was fired to cone 9 in reduction. It is about 4.5 or 5″ across, and not quite as tall as it is wide. The glaze contains 6.5% RIO and 4% Ceramic Rutile. The effect is vaguely similar to “hare’s fur”, but has its own character, which I rather like. It works moderately well in oxidation, but wants a soak to let the pinholes even out. In reduction, however, it is generally well behaved, as you can see. (I should point out that I sprayed the glaze onto this piece, in order to get a reasonably even coating thickness.)


         

(As usual, click either of the small images to get a larger version.)

For those who care: I ordinarily start mild reduction around 750° Celsius, and continue until approximately cone 6, basically the point at which the glaze has skinned over and further reduction becomes largely pointless (about 1220° C). I then reduce the gas flow until the flame is more or less neutral, and I keep it that way until the end of the firing, which is ordinarily at cone 10. (My test kiln is very small, and it heats up extremely rapidly; cone 10 is just shy of 1300° Celsius in most of my firings.) When I turn off the gas it takes me a few seconds to move the burner ( a forced-air design that I came up with in the process of converting the kiln from electric to gas) away from the inlet port, and during that time the kiln fills with air. This gives me a period of fairly strong oxidation just at and after peak temperature. Some glazes, for example Copper Reds, are noticeably brighter if you treat them that way.



This work is supported by
The Joss Research Institute
19 Main St.
Laurel  MD  20707-4303   USA





Contact Information:

Email: a@b.com, where you can replace a with my first name (jon, only 3 letters, no “h”) and b with joss.

My phone number is +1 240 604 4495.

Last modified: Sun Dec 2 23:30:25 EST 2007

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I am a Researcher of the Joss Research Institute. I work primarily on lasers and ceramics, with occasional excursions into other areas.

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