| Original Message: Re: "Scroddled" and "Agateware" but slip-casting different kettle of fish |
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Stefany, Now I see how you were talking about mixing slips. In my interest in the field of pottery, casting slips is a factory process almost completely unrelated to the art of the potter and kilnmaster. I lose nearly all interest in ceramics produced this way, although there can be much to be said of the decorator's art. I was not at all thinking about bead-making from clay slips, nor about polymer compounds. Sure your slip-mixing would reasonably relate to 'body' of beads. The matter of glaze and body is not nearly as simple as body vs. glaze, despite the efforts toward descriptive terminology. The ancient kilnmasters knew that in addition to temperature, duration of 'soaking' (as is said now) at a specific temperature and in specific atmospheric conditions have much to do with what happens on the surface as well as within the body of wares. By the way, whether the body is fired separately prior to glaze application and glaze firing, is very variable as to time, place, and ware. Some wares were fired multiple times: once for body and then several times for layers of glaze -- the famous almost mythical Ru ware of China appears to have been made in this way. Enamel-decorated porcelain could have been fired once for body and glaze maturation, then cooled and decorated with enamels which were again fired at a lower temperature. But the finest porcelain would have had separate firings for body and glaze. This was naturally a much more expensive process than the single firing of much glazed (or unglazed) earthenware and stoneware. Considerable effort and skill maintained specific atmospheric conditions at specific firing stages to produce such effects as the glorious blues and greens in certain ceramics. These conditions also affected underglaze decorations with copper-red and with cobalt. The same clay fired in high-oxygen or low-oxygen conditions will turn out different colors and different surface condition. The Chinese potters also varied kiln conditions from reduction (low oxygen) to higher oxygen (oxidation) conditions during the course of firing and cooling to produce specific effects. A lot of loose ash in the kiln will produce a glazing effect. Salt-glazed stoneware is the result of introducing regular NaCl to the kiln atmosphere at a given temperature stage of firing. Discussions on this board sure do cover a lot of ground. I wish you success in your bead work! Snap All rights reserved by Bead Collector Network and its users |
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