Lowell Ann Barron on sun 18 apr 04
Hi Ken and others. I have been wondering too. I have left mine open until the last 150 degrees and closed then in order to get it up to temperature without waiting too long which could greatly delay sleep.
Then I wonder at what point I should remove the peeps? Although I purposely did a slow cooling, I found that it was very slow...too slow...and even after the kiln was turned off it still took a looong time to be cool enough to open.
Another question is when it is OK to crack open the lid? Not that I am anxious to have a peak!
Thanks everyone, Lowell Ann
I do not have a kiln vent so I keep the
> peep holes open. At what point should I close them? Should I close
> them at all? One or both (it has two).
1
Kenneth Havens on sun 18 apr 04
I've been making pottery for quite some time but haven't ever had the
opportunity to fire my own work. Up to this point I've used kiln
sharing and not been able/allowed to participate in the firing process.
No complaints, everything has turned out well. Now I own a kiln and
am firing for myself, cone 6. I've had no problems with the bisque
firings, all goes well there, but my first glaze firing was a mixed
result. I was told that the top of electric kilns usually fires
hotter. Just the opposite happened to me, the witness cones showed the
bottom two shelves fired hotter than the top, the result on those
bottom two shelves was less than desireable, mostly pits and blisters.
I've gone over my firing schedule and everything looks good but I do
have a very simple question. I do not have a kiln vent so I keep the
peep holes open. At what point should I close them? Should I close
them at all? One or both (it has two). A simple question that I
haven't been able to find the answer to anywhere... books and
information just says "close peep holes" but doesn't designate when, at
what temperature, at what point in the firing... nothing. And not
having been present during firings I can't go from experience. So...
what's the general guideline and rule here?
Thanks,
Marcelyn
Snail Scott on sun 18 apr 04
At 08:46 AM 4/18/04 -0500, you wrote:
>...I was told that the top of electric kilns usually fires
>hotter. Just the opposite happened to me...
If we did a statistical analysis of every electric kiln
in use by a Clayart corrspondent, it may be that 'hot on
the top' would be slightly more common than not, but
statistical averages are only that - averages. The only
thing that counts is how YOUR kiln fires, and 'hot on the
top' is certainly NOT common enough to use as an initial
assumption. Depending on the condition of the elements,
cracks between rings, gaps in peephole plugs, irregular
loading, and variations in insulation, broad generalizations
such as the one you mentioned hardly ever hold true often
enough to be useful.
All my elements are different ages, and whenever I replace
one, the balance of heat changes slightly. No problem;
when the kiln gets close to final temperature, I back off
the elements in the hot section until it evens out, then
I kick it back into gear for the home stretch. Extra
insulation on the top and bottom has improved the evenness
of my firings significantly, however, and I seldom need to
'tweak' the elements anymore. An easy improvement!
Put cone packs in both high and low locations in your kiln.
Even if you can't see both during firing, you can compare
results afterward and decide how to proceed. A severely
uneven firng can often be the first sign of a failing
element.
>...I do not have a kiln vent so I keep the
>peep holes open. At what point should I close them?
Generally, you want them open during bisque, and during low
temperatures of glaze firings if there's anything needing
to be burned out. I put mine in around ^06 or red heat or
thereabouts for one-shot firings, and leave them out for
all bisque firings and 'icky' firings like overglaze lusters.
-Snail
Arnold Howard on mon 19 apr 04
Marcelyn, it is very good that you are using witness cones. Possible reasons
that your kiln fired cooler in the top:
1) The wrong element was installed. (I don't know what type of kiln you
have, so this is only a suggestion.) It is fairly common for kilns to have
more than one type of element. Most Paragon models have one type of element
in the top and bottom section and another type in the center section. If
these elements are installed in the wrong section, the kiln will not fire
evenly.
2) You may have had less ware in the bottom section. The lighter the ceramic
mass, the hotter that section of the kiln.
Some people leave the top peephole open during the entire firing, because it
lengthens the life of the Kiln Sitter. The fumes from the ware exit the kiln
through the top peephole rather than through the Kiln Sitter porcelain tube,
reducing corrosion inside the tube.
But you can insert the peephole plugs any time after the fumes have finished
burning off. During the first phase of firing, you should vent the lid by
propping it an inch or so and leaving the peephole plugs out.
Sincerely,
Arnold Howard
Paragon Industries, L.P.
arnoldhoward@att.net
----- Original Message -----
From: "Kenneth Havens"
I was told that the top of electric kilns usually fires
> hotter. Just the opposite happened to me, the witness cones showed the
> bottom two shelves fired hotter than the top, the result on those
> bottom two shelves was less than desireable, mostly pits and blisters.
> I've gone over my firing schedule and everything looks good but I do
> have a very simple question. I do not have a kiln vent so I keep the
> peep holes open. At what point should I close them? > Marcelyn
E. G. Yarnetsky on mon 19 apr 04
I would be suspicious of your elements if the top is underfiring.
Also, if the bottom is blistering, it may be because of the kiln
struggling for a long time trying to get the top to temperature. I
leave some peepholes out until around 1000 degrees so any water vapor
can escape. For me, a guess on when to put them in - others may do it
earlier or later. I leave the top one out until temp is reached as I
like to think it keeps the top of the kiln slightly cooler. At temp, I
put the last one in.
A kiln vent is a good idea in general. There are some horror stories
in the archives on carbon monoxide poisoning. Good ventilation in the
kiln room with open window, fans etc. is important, and essential if
you are working in there!
Best of luck!
Darlene Yarnetsky, Mudcat Pottery
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