Adding a little blue stain to a medium temperature transparent glaze can give it a more pleasant tone. Some iron is present in all stoneware bodies (and even porcelains), so transparent glazes never fire pure white. At cone 10 reduction they generally exhibit a bluish color (left), whereas at cone 6 they tend toward straw yellow (right). Notice the glaze on the inside of the center mug, it has a 0.1% Mason 6336 blue stain addition; this transforms the appearance to look like a cone 10 glaze (actually, you might consider using a little less, perhaps 0.05%). Blue stain is a better choice than cobalt oxide, the latter will produce fired speckle.
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