Gail Dapogny on wed 14 may 03
Hi Bruce,
We fire gas reduction to cone 9 over, 10 almost half over, about 12-13
hours after warming up.
To explain: I have come to believe that a12-13 hour firing is ideal, but
that is from about 700-800 f. We have an overnight warmup which takes us
to about those temps. Now, this is a 94 cub ft kiln. I would expect a
smaller kiln to reach those temps faster, -- although I suspect the slower
the better-- but I have no experience with a smaller kiln.
I was very taken by Val Cushing's recommended firing to be 8 hours from
body reduction to the end. Our body reduction starts at 012, which is
about 16-something, and occurs early afternoon . We check the flame and do
turnups as necessary each half hour. Just after body reduction, we have a
large jump in temp -- 90-110 per half hour, followed by some increases that
are only slightly lower. However, by the end of about 4-5 hours--- say
at about 2150 f-- our temp increase is down to about 40 or lower per half
hour, and it keeps on decreasing into the 2200s until it is stalled (soak)
at about 2280 f.--- cone 9 initially half over, cone 10 soft .The soak
goes on until 9 is well over and 10 is partially over ----45 min to over
an hour.
I don't know if 8 hours (from what temp??) is short, because of difference
in kiln sizes and starting temp.
I think this is a good Clayart question so I will answer the question as
far as my experience dictates both to you personally and to the list.
There are lots of firers on the list who are experienced with a variety of
reduction kilns, not just a large downdraft kiln such as I'm used to. I
love firing and involve myself as much as possible, but I have a ton of
stuff to learn. I listen and read as much as possible.
Gail Dapogny in Ann Arbor
>Hi Gail,
>
>Are you referring to gas or electric. If it is gas then my next question is
>pertinent.
>
>How many hours do you consider gas reduction firing times for shinos and
>reds to be to fall into the classification of short firing times ? Would you
>consider an 8 hour firing to cone 10 to be short?
>
>Hope all is well with you,
>
>bruce
Arnold Howard on mon 30 jan 06
The kiln may have a burned out element or switch. Here is a simple way to
test the elements:
1) Turn the kiln on high for about a minute.
2) UNPLUG the kiln.
3) Open the lid and place a strip of fax paper on each element for several
seconds.
5) If the fax paper strip turns dark, the element is okay. If the fax paper
doesn't turn dark, the element or switch may be burned out.
Sincerely,
Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com
----- Original Message -----
From: "gemma reddington"
> Hello everyone , me and my husband have brought a kiln out of the local
> paper , then i went to the local pottery supplies and brought some duncans
> paints etc and some cones.
>
> Last night i put the kiln on for out first test , with some pieces that
> were
> fired and all i did was underglaze them.
>
> As i havent really got a clue we started at 8.40pm i turned the klin to
> number one (its sliver and red hobbycraft kiln in the shape of a british
> fifty pence).
>
> I stayed up until three and kepted looking through the spy hole , but by
> this time i was so tired i went to bed , about 7.15 am in the morning i
> went
> to have a look and the cone still had not bent and i was so hot i turned
> it
> off because i wasnt sure how long it takes or if i was doing it right.
John McClure on sun 12 feb 12
I agree with Bill and you can check if they are dry by holding a small mirr=
=3D
or (or my glasses) at the top of the kiln when I lift the lid a bit.=3DA0 I=
f =3D
there is still moisture the glass will fog up and the 200 degree F hold tim=
=3D
e needs to continue.=3D0AJohn McClure=3D0A=3D0A=3D0A=3D0A__________________=
__________=3D
____=3D0A From: William & Susan Schran User =3D0ATo: Claya=
rt@L=3D
SV.CERAMICS.ORG =3D0ASent: Sunday, February 12, 2012 11:45 AM=3D0ASubject: =
Re: =3D
firing times=3D0A =3D0AOn 2/12/12 8:58 AM, "Kate Mondrone" OM> =3D
wrote:=3D0A=3D0A> ive been making pieces that have varied thickness ranging=
fro=3D
m 1/4" to 1"=3D0A> +/- thick.=3DA0 the clay is ^6 and im wondering how long=
to =3D
fire it each time=3D0A> in my electric kiln to prevent explosion.=3D0A=3D0A=
It is =3D
not the variable thickness that will cause your pieces to explode, it=3D0Ai=
s =3D
retained moisture/water of absorption. When the piece feels dry, let it=3D0=
As=3D
it an additional week to be sure it is completely dry. One might expect=3D0=
Ac=3D
racks to appear where a thick area abuts a thin area. If there is gradual=
=3D
=3D0Athick to thin then there will be less issues with cracking. To prevent=
=3D
=3D0Acracking, work towards and evenness all the way through the piece.=3D0=
A=3D0A=3D
I would suggest a very slow rise in temperature, 50F per hour to about 175 =
=3D
-=3D0A200F, then a 30 minute hold under the boiling point of water, all thi=
s =3D
time=3D0Awith spy hole plugs out and perhaps the lid propped open a bit.=3D=
0A=3D
=3D0ABill=3D0A--=3D0AWilliam "Bill" Schran=3D0Awschran@cox.net=3D0Awschran@=
nvcc.edu=3D
=3D0Ahttp://www.creativecreekartisans.com
ronroy@CA.INTER.NET on sun 12 feb 12
Hi Kate,
I fire sculptured life sized heads for a school class - about 30 heads
per firing - something they are more then 1.5 inches thick in places -
4 firings now now and no losses.
It's quite simple - no matter how dry they are - keep the temperature
under 100C (212F) till no more moisture come out the top spy with both
spy open - just hold a mirror or shiny cold metal in the hot air
coming out the top spy. When no more fogging there is no moisture left
in the kiln.
You can then fire as fast as you want.
RR
Quoting Kate Mondrone :
> ive been making pieces that have varied thickness ranging from 1/4" to 1"
> +/- thick. the clay is ^6 and im wondering how long to fire it each time
> in my electric kiln to prevent explosion.
>
Kate Mondrone on sun 12 feb 12
ive been making pieces that have varied thickness ranging from 1/4" to 1"
+/- thick. the clay is ^6 and im wondering how long to fire it each time
in my electric kiln to prevent explosion.
William & Susan Schran User on sun 12 feb 12
On 2/12/12 8:58 AM, "Kate Mondrone" wrote:
> ive been making pieces that have varied thickness ranging from 1/4" to 1"
> +/- thick. the clay is ^6 and im wondering how long to fire it each time
> in my electric kiln to prevent explosion.
It is not the variable thickness that will cause your pieces to explode, it
is retained moisture/water of absorption. When the piece feels dry, let it
sit an additional week to be sure it is completely dry. One might expect
cracks to appear where a thick area abuts a thin area. If there is gradual
thick to thin then there will be less issues with cracking. To prevent
cracking, work towards and evenness all the way through the piece.
I would suggest a very slow rise in temperature, 50F per hour to about 175 =
-
200F, then a 30 minute hold under the boiling point of water, all this time
with spy hole plugs out and perhaps the lid propped open a bit.
Bill
--
William "Bill" Schran
wschran@cox.net
wschran@nvcc.edu
http://www.creativecreekartisans.com
Steve Mills on mon 13 feb 12
Dear Kate,
Like you I make pieces of different weights and thickness.=3D20
As Bill said "dryness" is the key. My approach, particularly at this time o=
f=3D
year, is to set out my Bisque load on a bench, and direct three or four fa=
n=3D
s at it, at least overnight, sometimes for twenty-four hours, because as we=
a=3D
ll know the best drying day is a windy one.=3D20
For firing I believe you can't go too slowly up to visible dull red. Once t=
h=3D
ere I fire at 120oC per hour to the finish with the top spy open throughout=
t=3D
he whole firing to let out the sulphurous, fumes from the burning rubbish i=
n=3D
the clay.=3D20
Steve M
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my iPod
On 12 Feb 2012, at 13:58, Kate Mondrone wrote:
> ive been making pieces that have varied thickness ranging from 1/4" to 1"
> +/- thick. the clay is ^6 and im wondering how long to fire it each time
> in my electric kiln to prevent explosion.
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