Roger Korn on thu 29 apr 04
Karen and Ron,
I live in a dry part of AZ and use saltillos (chem-sealed) for
countertops and floors. The idea of using them as low-fire ware supports
occurred to me, so I bisque fired the bare tiles at a very slow rate.
Most of the tiles still cracked. Then I stuck a bunck of tiles in my
kitchen oven where the standing pilot holds the temp at about 170 F.
Left them there for a week. Weighed before and after - they lost about
4% weight through the oven drying. Fired them successfully after that.
My conclusion is that this is a weak terra cotta body that reabsorbs
moisture after firing and that they are failing from the vaporization of
the water absorbed in glaze application. Just a guess at this point, but
the long preheat seems to solve the problem.
Hope this helps,
Roger
--
McKay Creek Ceramics
In OR: PO Box 436
North Plains, OR 97133
503-647-5464
In AZ: PO Box 463
Rimrock, AZ 86335
928-567-5699
Ron Roy on fri 30 apr 04
Thanks Roger,
She did say the glaze was sharp at the cracks - that means they cracked
after the glaze melted and cooled so they are not cracking on the way up.
I would think - if you left your kiln on very low - say overnight - with
the lid open a bit - ot a vent system on - that would do the same thing as
well.
RR
>I live in a dry part of AZ and use saltillos (chem-sealed) for
>countertops and floors. The idea of using them as low-fire ware supports
>occurred to me, so I bisque fired the bare tiles at a very slow rate.
>Most of the tiles still cracked. Then I stuck a bunck of tiles in my
>kitchen oven where the standing pilot holds the temp at about 170 F.
>Left them there for a week. Weighed before and after - they lost about
>4% weight through the oven drying. Fired them successfully after that.
>My conclusion is that this is a weak terra cotta body that reabsorbs
>moisture after firing and that they are failing from the vaporization of
>the water absorbed in glaze application. Just a guess at this point, but
>the long preheat seems to solve the problem.
>
>Hope this helps,
>
>Roger
>
>--
>McKay Creek Ceramics
>In OR: PO Box 436
>North Plains, OR 97133
> 503-647-5464
>
>In AZ: PO Box 463
>Rimrock, AZ 86335
>928-567-5699
>
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Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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