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#21 Wyndham

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Posted 13 April 2017 - 06:50 PM

This is just a FYI. Star Ceramic supply in Star NC has a native high fire red clay called "East Fork", a clay mostly composed of a Catawba clay from upper NC clay used for generations for folk potters of the area. It burns dark brown in reduction, sandy and throws very well. It might be something worth looking into.

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#22 alexanderwilds

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Posted 14 April 2017 - 03:53 AM

I spent some time today with some Japanese potters who focus on shino in their work, checking on the above comments from yesterday, and have corrections and further info regarding Japanese Shino glazes.

 

1.  Glaze is mostly, like 95%+, feldspar, usually "Kamado" feldspar, a sort that melts to a viscous, semi-opaque, milky white.  Some clay is added, either kaolin, diatomacious earth, porcelain, or clay from the body of the vessel, as explained further below.  I add that the Japanese potters got into a serious debate regarding what they liked to add and how much, but it obviously is a matter of experimentation and desired effect.

 

2.  The idea is to match the melting point of the glaze to the firing temperature, so that the Shino glaze just barely melts, maybe  (thus the 10-day-long firing schedule).   The more clay you add, the higher the melting point, the more matt the surface, and, due to the increased shrinkage, the more cracks in the glaze.  The more clay you add, the sharper the edges of the cracks.

 

3.  To promote pinholes, the surface of the green ware is scraped while leather hard, roughening the surface.  This gives a solid mechanical bond to the glaze, and promotes the release of gases from the clay through the glaze, leading to pinholes and blossoms of colors from the clay body.

 

4.   To promoting crackling the surface, and to keep the glaze white,  the green ware is burnished,  allowing the glaze to slip, and maybe fall off, the surface.

 

Obviously, these glaze "flaws"  are what the Japanese potters are after - a feature rather than a bug.   I hope that helps.   Alex Wilds






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