[Clayart] ron roy, fast bisque

Snail Scott claywork at flying-snail.com
Sat Apr 14 12:26:28 EDT 2018

> On Apr 13, 2018, at 1:14 PM, mel jacobson <melpots at visi.com> wrote:
> …the critical time for burn out of gases and crap from bisque
> firing... final few hundred degrees...
> if that is the case...why not fire a bit faster..

I am of the same opinion. I do a pretty long candle phase, as it doesn’t cost much in power or fuel to go low and slow below 200F. I let it creep up past 400F, as I’m assuming that some parts of my work (thick sculpture with interior structure) aren’t necessarily past 200 just because the outer surfaces are. From that point, I generally kick an electric kiln straight to ‘high’. I’ve never met a standard electric kiln that could fire fast enough to be ‘too fast’, even if I wanted it to. (With a fuel kiln, it’s easier to overdo.) Desired absorption level ought to be the main determinant of bisque temp, I figure; clean burnout can be achieved ether through temp or time. I figure it’s a tradeoff at the top end of bisque: whether to fire hotter or slower. Hotter is easiest if you kiln hasn’t got a controller, but It’s not tough to just turn everything to ‘medium’ after it hits temperature, though, and extend the period spent in the burnout range without significantly increasing heat-work.  Electric kilns wth controllers are even easier - either program in a slower ramp right at the end, or a soak at the end of a preprogrammed schedule. 

My usual sculpture clay is pretty clean and open, and I seldom use glazes that care about crud, so ^08 or ^010 are adequate, and I often single-fire. The clays I supply my students is ‘tight’ and much dirtier, though (Laguna’s #55, or L&R’s midrange white), and need a good burnout. We only have class every other day, so I usually just set the kiln to the preprogrammed ‘slo bisq’ schedule. When I use similar clay in my own studio, I want faster turnaround, though, so in between slow candling and slow peak soak, I just crank it, with no ill effects.

Snail Scott
claywork at flying-snail.com

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