Paul Herman on fri 5 aug 05
clay
Hello Mary,
Here's what I advise you to do. You should fire the clay to the
recommended cone. That way it will (hopefully) have the right porosity
and fired hardness.
You could fire a cone 10 clay to cone 6 and it might work ok but the
clay would be "underfired" and may be somewhat porous.
If you fire a cone 6 clay to cone 10, it may be "overfired" and get too
soft, causing slumping, warping or bloating.
So the answer is yes, you can do that, but there are dangers that lurk
in those possibilities. And we get back to: Clays should be fired to the
cone they are formulated for.
The "Potter's Dictionary" by Hamer and Hamer is a great book, if you
don't have it in your pile of 40 books, it's a good one to add.
Best,
Paul Herman
Great Basin Pottery
Doyle, California US
http://www.greatbasinpottery.com/
----------
>From: Mary/Adams
>To: CLAYART@LSV.CERAMICS.ORG
>Subject: Continuing Newbie Questions - firing differrent cone than cone of clay
>Date: Fri, Aug 5, 2005, 4:26 PM
>
> Hi everyone! Can one take a Cone 10 bisque-fired piece and glaze it with
> Cone 5-6 glaze and fire at Cone 5-6? AND can one take a cone 6 fired piece,
> glaze with cone 10 glaze and fire at cone 10? I've looked all over for
> these answers and maybe they are there; but, haven't found them.
>
> Thanks to anyone for answers again.
>
> M
Snail Scott on fri 5 aug 05
clay
At 04:26 PM 8/5/2005 -0700, you wrote:
>Hi everyone! Can one take a Cone 10 bisque-fired piece and glaze it with
>Cone 5-6 glaze and fire at Cone 5-6?
You mean that the bisque firing went to ^10?
Or that it was a ^10 clay fired to a typical
(^08-^04) bisque temperature?
If it's been fired to ^10, you can still glaze
it, but getting the glaze to stick is the hard
part, since the clay won't be absorbent anymore.
Heating the clay is one way to help, and other
folks like to add wallpaper paste to the glaze
to help it stick.
If it's just a ^10 clay bisqued to normal bisque
temperatures, you can glaze normally, but remember
that a ^10 clay will not be properly vitrified at
^6. The ^6 glazes will tend to craze because of
this, and the clay will be weak.
>...AND can one take a cone 6 fired piece,
>glaze with cone 10 glaze and fire at cone 10?
A true ^6 clay will tend to warp and slump at ^10,
and may even bloat. (If it doesn't, then it wasn't
really a ^6 clay, but one that the manufacturer
merely called a ^6 clay. All too common.) And if
it's got a ^6 glaze on it already, it will probably
run.
You can always re-fire anything to a lower cone
with glazes appropriate to that temperature, but
you generally can't re-fire hotter unless it was
underfired to begin with.
-Snail
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