|Monthly Tech-Tip |
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The walls are very thin, yet no trimming was done to make them thin. Why? It is super plastic. Others claim to be plastic, but they use the word in a relative sense. They mean a little less flabby than other flabby porcelains! Polar ice, when it has the right water content (dewater it on a bat if needed), is tough enough to throw as large as even the most plastic stonewares. It might seem impossible that a body this translucent can be as plastic as it is and as stable in the kiln as it is. Want to know it’s recipe? Search around on this site and you will find clues in a number of places, put them together, do a little testing, and derive it yourself!
The Polar Ice data sheet has been changed. In the past we have been hesitant about firing it over cone 6. This is because it is just so vitreous and translucent that firing it higher seemed to be asking for trouble (like warping, blistering). But at cone 10R it is still resistant to warping. And fires this beautiful blue-white. The translucency, amazingly, is about the same: Incredible! This is among the most incredible pieces we have ever made in the studio here, it is hard to believe it is possible produce this kind of quality in a pottery studio.
These are two cone 6 transparent-glazed porcelain mugs. On the left is the porcelainous Plainsman M370 (Laguna B-Mix 6 would have similar opacity), it is semi-vitreous and has no translucency. Right is a highly vitreous, New Zealand kaolin based porcelain, Polar Ice. The secret to making this porcelain super-white is the NZ kaolin. The secret of its impossibly-high plasticity is the very expensive plasticizer, VeeGum T. What about the translucency? Nepheline syenite is used as the feldspar, but it alone cannot deliver this kind of translucency at cone 6. Amazingly the 4% Veegum acts as a translucency catalyst, it is the secret. Commercial manufacturers could never use a sticky and difficult-to-dry porcelain like this, but a potter can do incredible things with it (e.g. throw thinner, lighter, bigger than any other clay he/she has ever used!).
Made using porcelain fired to cone 11+. This is a splendid demonstration of translucency. Without a back-light it is just a white slab. But the varying thickness in the porcelain determine the amount of light that passes at any given spot, thus producing the design.