Lisa E on sun 5 nov 06
I just acquired an old manual kiln (pyrometer only) and wanted to confirm
the following:
Bisque firing to Cone 08 -
Q1- How long should this process take? I already found great resources on
this site but my guess is from the time I turn my kiln on until it reaches
Cone 08 (1692 F) it should take 9 hours (not including cooling time). Is
this too fast? Especially if I have thin and thick pieces?
Glaze firing to Cone 6 - This is where I cannot find any solid info.
Q2 - How long should this take?
Q3 - How slow should I ramp up the temp before it reaches Cone 6 (2165 F)?
Q4 - When it reaches cone 6, should I set my kiln on the lowest setting for
1 - 2 hours to let it soak and then turn off the kiln and let it cool?
Thank you in advance for your tips and advice. I searched this site high
and low before posting but couldn't find solid answers.
Best Regards,
Lisa E
Snail Scott on mon 6 nov 06
At 08:40 AM 11/5/2006 -0800, you wrote:
>Bisque firing to Cone 08 -
>Q1 - How long should this process take? ...my guess is...it should take 9
hours...Is
>this too fast? Especially if I have thin and thick pieces?
Sounds like a reasonable time, unless the
thick stuff is _really_ thick. (3/4" +) If
you don't get bad results on the glaze firing,
it's probably fine.
>Glaze firing to Cone 6 -
>Q2 - How long should this take?
>Q3 - How slow should I ramp up the temp before it reaches Cone 6 (2165 F)?
>Q4 - When it reaches cone 6, should I set my kiln on the lowest setting for
>1 - 2 hours to let it soak and then turn off the kiln and let it cool?
Firing up: if the work is bisqued already,
go ahead and fire it as fast as the kiln
will go. (It's electric, yes?) I give mine
15 minutes on each power setting just to
avoid slamming the elements straight to
high, but an electric kiln of the normal
sort really can't fire too fast for
bisqueware. No ramp needed; just go.
Warning: if you use an underglaze or engobe
on greenware, a full, semi-vitrified
coating of it can prevent glaze moisture
from escaping easily. For such work, add
a several-hour candle before firing.
Whether you do a controlled cool-down (or
a soak) depends entirely on your glazes.
Some glazes need a nice long soak,
especially if the firing was fast. Gloss
glazes should be cooled quickly, to
prevent crystal growth. For these, just
turn the kiln off. Slow cooling is needed
for microcrystalline matte glazes to
develop properly, or else they may stay
glossy. (An adequately insulated kiln may
cool slowly enough by itself, but most
electrics are not in that category.) As
you can see, no one firing schedule is
right for every glaze.
The clay doesn't care so much. If you
aren't using any glaze, let it cool
naturally.
However...you said you have a pyrometer
only? These can be VERY deceptive with
fast firings (or very slow ones). Make
sure you also use witness cones, to tell
you what's really happening in terms of
heat-work. Temperature alone not enough
information.
-Snail
Lisa E on mon 6 nov 06
Thank you so much for the advice!!! Lisa
On 11/6/06, Snail Scott wrote:
>
> At 08:40 AM 11/5/2006 -0800, you wrote:
> >Bisque firing to Cone 08 -
> >Q1 - How long should this process take? ...my guess is...it should take 9
> hours...Is
> >this too fast? Especially if I have thin and thick pieces?
>
>
> Sounds like a reasonable time, unless the
> thick stuff is _really_ thick. (3/4" +) If
> you don't get bad results on the glaze firing,
> it's probably fine.
>
>
> >Glaze firing to Cone 6 -
> >Q2 - How long should this take?
> >Q3 - How slow should I ramp up the temp before it reaches Cone 6 (2165
> F)?
> >Q4 - When it reaches cone 6, should I set my kiln on the lowest setting
> for
> >1 - 2 hours to let it soak and then turn off the kiln and let it cool?
>
> Firing up: if the work is bisqued already,
> go ahead and fire it as fast as the kiln
> will go. (It's electric, yes?) I give mine
> 15 minutes on each power setting just to
> avoid slamming the elements straight to
> high, but an electric kiln of the normal
> sort really can't fire too fast for
> bisqueware. No ramp needed; just go.
>
> Warning: if you use an underglaze or engobe
> on greenware, a full, semi-vitrified
> coating of it can prevent glaze moisture
> from escaping easily. For such work, add
> a several-hour candle before firing.
>
> Whether you do a controlled cool-down (or
> a soak) depends entirely on your glazes.
> Some glazes need a nice long soak,
> especially if the firing was fast. Gloss
> glazes should be cooled quickly, to
> prevent crystal growth. For these, just
> turn the kiln off. Slow cooling is needed
> for microcrystalline matte glazes to
> develop properly, or else they may stay
> glossy. (An adequately insulated kiln may
> cool slowly enough by itself, but most
> electrics are not in that category.) As
> you can see, no one firing schedule is
> right for every glaze.
>
> The clay doesn't care so much. If you
> aren't using any glaze, let it cool
> naturally.
>
> However...you said you have a pyrometer
> only? These can be VERY deceptive with
> fast firings (or very slow ones). Make
> sure you also use witness cones, to tell
> you what's really happening in terms of
> heat-work. Temperature alone not enough
> information.
>
> -Snail
>
>
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