Stop a runny glaze with another glaze!

This iron red cone 6 glaze, G3948A, is applied thickly and runs during firing. With no countermeasures, it ends up on the kiln shelf (like the one on the left). Since this glaze breaks-to-black where thin on the edges of contours, glazing the base black seems like a natural match. The base of this was first dipped in G3914A black, up to about 1 cm (1/2 in). I then waxed over all of the black up to within 1-2mm of its edge. Then I applied the iron red by dipping in the normal way for liner glazing mugs. For this thickness of the brown the black melt is able to catch and stop it within 5mm or less.

Related Pictures

Iron red on porcelain and a red burning stoneware

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This is the G3948A recipe fired to cone 6 using our standard C6DHSC schedule. The color "breaks" to black where thinner around contours so it seemed like a natural that the inside glaze should be G3914A Alberta Slip black. The contour of the foot ring is important or the glaze will run onto the kiln shelf. My standard fluted ring foot is working well. An option would be to glaze the bottom inch or so with the black and the iron red down to that.

High melt fluidity is required to achieve the visual effect of this glaze

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This is G3948A, an iron red cone 6 glaze. The reason for the variegated surface is the high fluidity of the melt. Adequate thickness is also important, enabling it to run downward to some extent. That means this is not actually over fired. Using it thus requires consideration of the running behavior, accommodating it in the shape of the ware on which it is used. Obviously, using this on the insides of pieces would result in pooling at the base, that would likely produce glaze compression, cracking the piece during cooling.

A way to prevent a tenmoku glaze from running onto your kiln shelves

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Tenmoku reduction fired glazes can be so beautiful yet few people use them. Why? The melt fluidity is the key to their appearance but also the curse. They pool on inside bottoms producing glaze compression issues. Runs stick pieces to the kiln shelf. They stretch thin over rims roughening them with any grit from the body or glaze materials. All three issues have a simple solution: The GR10-A base as a liner glaze that wraps over the rim and as a “catcher glaze” at the bottoms. I use a dipping glaze version of it for the insides and a brushing glaze version for the bases (and up the side walls about 1cm). The tenmokus GR10-K1 (left) and GA10-B (right) can be applied thicker than I would otherwise dare and it’s no problem, that 5mm of catcher glaze is all it takes to stop the running. Another benefit: Now it is also possible to use these glazes on stonewares, not just porcelains.

Links

Glossary	Fluid Melt Glazes Fluid melt glazes and over-melting, over fired, to the point that they run down off ware. This feature enables the development of super-floss and cyrstallization.

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