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black and red terra sigs

updated fri 31 jan 97


Vince Pitelka on tue 14 jan 97

>Vince: I don't work at this temp.,and I therefore am only speculating.
> Could it be that red clays, being more fusible at lower temperatures do not
>accept carbon in the reduction as readily as ball clays that tighten up at
>much higher temps?
>Craig Martell-Oregon

Thanks to Craig and Russel and others who posted this suggestion. I had
thought about this, but I only bisque to 1230 F in an electric kiln, which
is high enough for minimal sintering but with no shrinkage at all, so it
should not tighten up the surface in either sig. I bonfire the pots within
a steel cage surrounded by fire, and I build up the fire until the steel is
glowing dull red. I allow the flames to die down a bit, and then smother it
with crushed manure and then sand/ash mix. I am using a very refractory
body, and the pre-bisque and the bonfire never get hot enough to cause any
shrinkage to speak of beyond the bone-dry stage. If the sig coating was
shrinking more than the body, it would crack, and it doesn't. This is no
big deal. I love the blackware-fired color of both sigs, but it does
intrigue me.
- Vince
Vince Pitelka - vpitelka@Dekalb.Net
Phone - home 615/597-5376, work 615/597-6801
Appalachian Center for Crafts, Smithville TN 37166