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pit fires and cracks/add pumice

updated fri 26 feb 99


Marcia Selsor on thu 25 feb 99

Wegde in some pummice-this is what N.A. in the SW used as a fine
aggregate. This will help with any thermal shock and not hinder
burnishing.Could be the pellets. I never tried them. I use paper.
kindling and sawdust, fine sawdust. Burn it slow. I use a 55 gallon drum
with 18 one inch holes which are plugged and unplugged depending on the
need for air. Piepenburg has a good little film on sawdust firing.
Marcia in Montana

Ray and Claudia wrote:
> ----------------------------Original message----------------------------
> Hi all...
> I just unloaded another pit firing and lost 3 out of 6 vessels. I am
> not happy with those percentages, and wonder...can we talk!
> I am using Warm Springs Red...a typical low fire earthenware, which I
> first bisque to ^06. These vessels are burnished, so this is as high as
> I dare to bisque. My fuel is a mixture of sawdust, wood pellets, and
> various combustibles from around the landscape. When I used Raku clay,
> I had very little breakage (but I could not burnish), and I realize that
> this red clay is tighter and more prone to disaster than that Raku
> clay. Still...I should be able to do better. Should I fire fewer
> pieces at one time...I fire 6 usually, three above, three below. The
> breaks are not consistent as to position in the kiln, so I do not have
> problems with the vessels falling into each other. I have not been
> diligent about filling the insides and wonder if this could be part of
> the problem. We have been having a lot of wind, but the outside
> temperature is not awfully cold here these days...around 50 degrees. I
> did not open the kiln until it was totally cold....just to prevent the
> cracks! Of course, it was the larger vessels that cracked...which could
> also be part of the problem. I just wonder if anyone out there has had
> this problem and has minimized it in any way. Thank you!
> Claudia

Marcia Selsor