[Clayart] pin holes

Snail Scott claywork at flying-snail.com
Sun Jul 7 09:58:33 EDT 2019

Different clay bodies require different bisque firings. 

The midrange commercial off-white stoneware I use for my students requires a solid ^04 bisque to avoid pinholes. Although rated for ^5, I consider it to be properly vitrified at a high ^6 or low ^7, so a higher bisque also reduces absorbency, permitting easier brush-glazing. I have also switched from using the electric kilns’ pre-programmed ‘slow bisque’ schedules (which seem overly conservative to me) in favor of a faster firing but with extra candling time and a soak at the end. Equally good results, but a quicker turnaround that suits the college class schedule...no need to unload with gloves. 

I also use a midrange commercial off-white stoneware for my own work, but it’s a world away in terms of firing properties.  It’s a coarser, cleaner body (with lots of grog and minimal carbon), so a fast low bisque to around ^010-08 is ample, with no soak. I’ve had no difficulty with glaze flaws, even though I often don’t bisque at all and glaze as greenware for single-firing. I still candle long because I work thick, even though open bodies like this one tend to dry easily, and the power usage on a single ‘low’ element is negligible. 

Two mid-range off-white stonewares manufactured by the same company; two completely different bisque protocols!  There is no single correct process.

Snail Scott
claywork at flying-snail.com

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