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Post by roberttroost on Sept 29, 2017 13:10:10 GMT -6
I've used both, but mostly a custom porcelain these days. I think the answer here is highly dependant on the porcelain body. I had different results with the laguna cone 10 porcelain than with my current porcelain. Using a porcelain slip over the bmix is a good way to get the best of both worlds. Hey Adam. I,ve been using B-mix all these years with pretty good results.While I would love to try any porcelain,I won,t because I have a $7000 peter pugger that the acid in the porcelain clay would eat the the aluminum mixing chamber,would have to buy one with a stainless steel chamber and can,t really afford to spend that much money again.Oh well maybe I,ll try some soon and just hand wedge something I haven,t done in 35 years,probably put air into instead of wedging it out.Hope you and your family are well.LTR.
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Post by tileman2 on Sept 29, 2017 19:36:04 GMT -6
Robert:
If I could add a correction: porcelain bodies typically run from 8.25 to 8.50 PH: alkalinity. Clay bodies started using Nep Sy as a flux a little over a decade ago because Custer became an unstable market. Both porcelain and stoneware bodies were mostly potassium based until the switch to sodium. Nep Sy has a soluble sodium content between 14-20%: which is the basis of corrosion and pitting. when sodium hits water, hydrolysis occurs, and the soluble salts become hydroxides: highly caustic to aluminum. The problem now, most stoneware bodies are switching to Nep Sy as well, so it likewise will cause pitting problems. Sodium also contributes to rapid drying, and also has the tendency to resist homogenous blending in clay bodies. Nep Sy based porcelain bodies also tend to over nucleate, and are more susceptible to pin hole issues because of higher incidents of off gassing. It is the sulfur content: sulfides and sulfates in stoneware that interfere with crystal development.,
Porcelain bodies that are deeper tan or deeper grey colored have higher percentages of ball clay content. As ball clay in general get darker brown, or darker grey in color: the higher the sulfur/carbon content they have. OM4 for example has less than 200 ppm of sulfur content, while Bell Dark has nearly 500 ppm of carbon. Grey colored ball clays have high levels of sulfides, in addition to higher levels of titanium. So even porcelain bodies can have vast differences in crystal formations. Grolleg has been the standard for crystalline use: better known as Coleman porcelain. NZ kaolin is the cleanest, but does not tolerate cone 10 very well, and plasticizers become critical when blending. Try using Mahavir potash, Kona or minspar: which is more crystalline friendly. Nep Sy has become popular because it is one third the cost of potassium.
Tom
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