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Basalt as Colorant in Celadon Glazes

Basalt as Colorant in 2 Base Recipes.

Basalt as Colorant in 2 Base Recipes.

More local Basalt. Here used as colorant in high fire celadon glazes. On the top left, the raw material which was collected from various places throughout Idaho and Utah (and all mixed together), bottom left the homogenous, calcined, milled, sieved, and dried material ready for glaze.

In this set the basalt is supplying the iron necessary for that timeless celadon blue. Its also bringing significant additions of magnesium and calcium to the recipe. The % of basalt here ranges from 0 to 10% in 2.5% steps – applied to a dark stoneware and porcelain tiles.

This series were fired in a very fast and simple cone 10 reduction firing with a very basic reduction cool. 6 hours start to finish, in a small fiber test kiln — Heavy body redux for 30 min @ ^012-^08, then light redux to ^6, then a medium redux to ^10. At soft cone 11 I crash cooled a few hundred degrees, turned the air and gas down, dampered in, and put the kiln into about a -4°/minute cool, periodically opening the door to quickly crash cool -30 or -50 degrees until 1400, then shutting everything off. In some cases reduction cooling will effect the color and quality of the glazes significantly, but here it only effected the stoneware – keeping the iron oxide on the surface in its black reduced form. A good reduction firing will yield these glaze colors with no special effort cooling – here the RC was strictly for a darker stoneware color.

The Recipes

Fiske’s Tichane Chun
Custer Feldspar 48
Silica 31
Calcium Carb. 20
Bone Ash 1
(Iron Oxide 1.5)
— A range .5 to 3% Iron Oxide gives a similar spectrum of blue as the basalt does here – different flavors of Iron bearing materials yield different flavors of glaze, obviously. I’ve tried probably more than 50 kinds of iron over the years – try what you have and figure out what flavor you like best!

Fiske's Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.

Fiske’s Tichane Chun with 1.5% Red Iron Oxide. Fired to C10 in Reduction.

Fiske’s (Pinnell Clear) PC Celadon
Custer Feldspar 25
Grolleg Kaolin 20
Calcium Carb. 20
Silica 35
(Spanish Iron Oxide .85)

Fiske's PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.

Fiske’s PC Celadon with a range of 0%-2.55 Red Iron Oxide. Fired in C10 Reduction.

 

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5 thoughts on “Basalt as Colorant in Celadon Glazes

  1. Pingback: Clay Blog Review: February 2016 - Pottery Making Info

  2. Hey Matt, thanks so much for this blog – a great repository of info for the aspiring potter!

    I was wondering – is a reduction atmosphere necessary for these glazes or would they work in oxidation too?

    • For these glazes, and any ‘real’ celadon, a reduction atmosphere is essential. You can certainly fire them in oxidation, but the colors will be clears and yellows and browns – and not that nice!

      • Aha! This explains a lot – my experiments in an oxidation atmosphere have been less than spectacular.

        Your exhibition statement makes for great reading, by the way. Thanks for posting it.

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