Centa Uhalde on sun 26 nov 06
I am trying to understand the firing instructions for a glaze I want to try
in the archives. These are the instructions, (I'm concerned only with
Farenheit) and the third line doesn't make sense to me. Could someone
enlighten me? They are instructions for a butterscotch glaze:
Firing ramp with an electric controller is:
100c p/h to 600c (212f - 1112f)
150c p/h to 1140c (302f - 2084f)
80c p/h to 1220c (176f - 2228f)
15 min. soak
cool down max. to 900c (1652f)
Hold 1 hour
Shut off kiln
Thanks,
Centa
Snail Scott on sun 26 nov 06
At 02:47 PM 11/26/2006 -0800, you wrote:
>I am trying to understand the firing instructions for a glaze I want to try
>in the archives. These are the instructions...
>100c p/h to 600c (212f - 1112f)
>150c p/h to 1140c (302f - 2084f)
>80c p/h to 1220c (176f - 2228f)
>15 min. soak
>cool down max. to 900c (1652f)
>Hold 1 hour
>Shut off kiln
Seems pretty straightforward; nothing=20
odd about the third line that I can see.
I do note that the fahrenheit equivalents=20
are written as:
(212f - 1112f) and so on,=20
and it probably would be clearer to say:
(212f p/h to 1112f) and so on
which means:
(212 =BAF per hour up to 1112=BAF) and so on,=20
mirroring the the celcius directions.
So, you will fire at a moderate speed up=20
to 1112 degrees Fahrenheit, then fire=20
faster up to 2084 degrees Fahrenheit, then=20
a bit slower 'til you hit temperature.
Frankly, the speed that the kiln climbs at=20
is almost irrelevant for most glaze firings,=20
since the glaze layer is mighty thin and=20
especially since most electric klilns can't=20
fire very fast even if you tried. Speed of=20
firing matters mainly to the clay, which is=20
thicker and not a liquid and needs time to=20
burn out, and vitrify. With glazes, the=20
only things that really matter are the time=20
they spend above their melting point at the=20
top of the firing, and the time they spend =20
around the crystallization point on the=20
way down.
The important parts of this schedule -=20
the only parts that really matter much to=20
a glaze - are the soak and the cool-down=20
parts of the schedule. For the first part,=20
on the way up, just fire as your would=20
normally; don't sweat that part.
-Snail
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