Bruce Girrell on wed 4 apr 01
Carole -
When applying horsehair decoration, the pots are typically fired to about
650 oC (1200 oF). This is about cone 020 or 019. At that temperature you
should not be losing the burnish.
When getting that bank loan for the new studio, use some of the money for a
pyrometer. Most people swear by a digital pyrometer, but I use an analog,
since absolute accuracy and precision are not essential. Since the horsehair
decoration does not require any maturation of the clay body, heat work
(measured by the cones) is not an issue. Raw temperature, as indicated by a
pyrometer, works just fine.
After you have applied the decoration, cooled the pot, and cleaned off the
mess, wax the pots using a hard paste wax. If the surface was burnished, the
wax will bring up a beautiful shine.
In answer to some of your other questions -
1) Yes, you can use small cones, but remember that small cones assume a
different temperature rise rate and indicate a different temperature than
their larger siblings.
2) You can make cone packs for rapid firing by mixing a lot of vermiculite
into the clay used to support the cones and then drying the packs thoroughly
(in an oven, if necessary) before firing. There are also cheap wire holders
available for cones. Each holder holds one cone and you sometimes have to
get a little aggressive to get a melted cone separated from the wire after
firing, but they work OK in a pinch like this.
Bruce "whinny, neigh, cough, cough, cough" Girrell
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