firing speed

I have an electric kiln and bisque fire to cone 04 on slow speed, and glaze
fire to cone 6 (also slow). Is it really necessary to bisque fire on slow?
I understand the reason for glaze firing on slow speed, but not bisque.

Thanks
Betsy

Betsy:
The only real reason to fire slowly is to get the piece(s) past the point of
water conversion to steam at 100C (212F), and the silica inversion at 600C.
Once these two points have been passed, you can fire as slowly or as fast as
you like. I regularly fire to cone 10 in less than 7 hours (porcelain)

More important is slow cooling, especially through these two temperature
points again.

Hope that helps,

--
Wayne Seidl
Key West, Florida, USA
North America, Terra
Latitude 81.45W, Longitude 24.33N
Elevation 3.1 feet (1m)
"Richard" wrote in message
...
I have an electric kiln and bisque fire to cone 04 on slow speed, and
glaze
fire to cone 6 (also slow). Is it really necessary to bisque fire on
slow?
I understand the reason for glaze firing on slow speed, but not bisque.

Thanks
Betsy

"Richard" wrote in message
...
I have an electric kiln and bisque fire to cone 04 on slow speed, and
glaze
fire to cone 6 (also slow). Is it really necessary to bisque fire on
slow?
I understand the reason for glaze firing on slow speed, but not bisque.

Thanks
Betsy



It is very necessary to fire slowly in a bisque up until 600C. I increase
temp by 100C an hour until 600C then I set my kiln to flat out with half our
soak. That is as fast as it can go.
If you go too fast in this first 600 degrees you will have cracking
exploding and just general breakage.
Glazing, unless you are doing crystaline glazes or similar slow firing is
not necessary. I increase at 150C per hour until 300C then flat out with
half hour soak. The important thing with a glaze firing is gaining the
amount of heat work required for the glaze to mature. A cone is just
actually measuring the heat work. So you need to calibrate your kiln, that
is do a number of firings at your different temps or what you think is your
desired cone with cones top bottom and middle. When you require a C6 you
would have a cone 51/2 cone 6 and cone7 in all three places. When you have
completed that you will have more idea what your kiln is actually doing.