Paulette Carr on sun 11 jul 04
I hope that someone can answer this question for me.
Situation: I just unloaded my kiln after a bisque fire to ^04. Since last
winter, I have been using a top temperature of 1915=9AF with a hold time of 1=
5
minutes. I fire very slowly up and down. Usually, all cone packs show ^04
down & ^03 at an angle of approx. 20=9A (or 2:00), and the firings have been
very even. The kiln was arranged, with regard to furniture, pots, and tile=
s
as usual -- nothing different. On the bottom and top shelves, the cone
packs, however were showing that ^04 was not fully down, but rather at
slightly greater than 80=9A, by the Orton template. The middle shelf was as
usual. I thought that perhaps my elements might be changing, but when I
looked back at my old firing logs (when the elements were newer) I found th=
e
same trend, only more underfired last July and August when it is very humid
here. At that time, I increased the temperature and hold time to 1925=9AF an=
d
20 minutes to achieve a fully ^04 even firing. I found later, in the winte=
r
(when we have much lower humidity), that I had to decrease the top
temperature and hold time to the values first mentioned. It has been very
humid here with all the storms, resulting in parts of my studio floor
getting wet, and the ac off ... so my studio is humid.
My question: Does the humidity or season change the parameters
(temperature and time at a temperature, and rate) that affect heat work?
Unfortunately, I only have a little more than a year's good data on this
kiln, and I have only become fastidious about using cone packs in the last
couple of years. I realize that this is only one firing, but my kiln has
been a champ and extremely predictable up until this time. It is important
that I don't under, or overfire the glazed pieces ...
Thanks for your thoughts on this topic.
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member/Potters Council
Cindi Anderson on mon 12 jul 04
Hi
I can't answer humidity specifically. But usually when it is humid it is
hot. It is very common for power to drop during the summers when everyone
runs their air conditioning. It might only be a few volts which doesn't
affect other appliances, but makes a difference to a kiln. Every summer
there is a rash of people saying their kiln is firing slow, isn't getting up
to temperature, etc.
Personally I think the only foolproof method is to watch the cones as they
drop and turn the kiln off when you see it is time. If your glazes mature
over a wide temperature this might not be necessary, but if not of if you
want exact replication of your glazes that is what I would do. Then you are
not guessing at how the loading or voltage is going to affect the firing.
Cindi
Fremont, CA
----- Original Message -----
From: "Paulette Carr"
I found later, in the winter
(when we have much lower humidity), that I had to decrease the top
temperature and hold time to the values first mentioned. ...
My question: Does the humidity or season change the parameters
(temperature and time at a temperature, and rate) that affect heat work?
Kathi LeSueur on mon 12 jul 04
paulette_carr@DSLEXTREME.COM wrote:
>I hope that someone can answer this question for me.......
>
>
>My question: Does the humidity or season change the parameters
>(temperature and time at a temperature, and rate) that affect heat work?>>>
>
While I fire with gas, I find that humidity can have a great affect on
firings. My kiln log now includes not only temperature and weather
conditions, but humidity and barometer readings. It really helps me to
stay cool headed and do the right thing when the kiln starts acting
wacky, stalling and taking an incredible amount of time between cones.
Good records help to have consistant firings.
Kathi
>
>
>
John Rodgers on mon 12 jul 04
Paulette Carr wrote:
>I hope that someone can answer this question for me.
>
>
Paulette,
I can't answer your question directly but I have been firing my old
Crusader Kiln for number of years and I fire it with the bottom plug
out always. When the firing is done, I put the plug in for the cool
down. I learned this little trick from an ceramics oldtimer a long
time ago and ever since I have always gotten good firings regardless of
what the weather was like.
To this add the fact that I always fire using a free standing witness
cone. I watch for it to bend to the right position and then I turn off
the kiln. I do not depend on a kiln sitter. I have found that my firings
are better by doing it manually. My primary glaze is Floating Blue, a
finicky glaze, but since I have gone to doing a manual shutoff of the
kiln, and using a witness cone to tell me when to shut it off, my glaze
firings of Floating Blue are perfect everytime. The length of time for
the firing may vary depending on the load, but the heat work required is
always the same, and the witness cone VISUALLY tells me when it's done,
and I turn off the kiln. No controller can get it better than that.
Regards,
John Rodgers
Chelsea, AL
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