Kenny MacDonald on sat 1 nov 97
For years I have been religious about opening my glaze firing no earlier than
90^ or less. Even then, I let the ware cool down to room temp. But when doing
a large bisque firing ( getting ready for a show and wanting to push the
limit) I am tempted to throw open the kiln lid at 300^ + and just let it
speed cool. What is the possible limit and probable damage that I could
incur? Thanks KEN
Bradford on tue 4 nov 97
Kenny MacDonald wrote:
>
> ----------------------------Original message----------------------------
> For years I have been religious about opening my glaze firing no earlier than
> 90^ or less. Even then, I let the ware cool down to room temp. But when doing
> a large bisque firing ( getting ready for a show and wanting to push the
> limit) I am tempted to throw open the kiln lid at 300^ + and just let it
> speed cool. What is the possible limit and probable damage that I could
> incur? Thanks KENHi Ken,
I admit I really don't know what the limits are of kiln openings. Here
in our studio we are always behind and need to push the next glaze load
thru the kilns so we need to speed cool. I suspect that I'm going to be
hollered at by some folks out there for this but it works for us. We
crack the lids of our electric kilns at 1000^ (opened about 1/2"). At
650^ its opened about 2-3". At 450^ the lid is opened completely.
We've been doing this for about four years without any mishap (we fire
to cone 6). Our gas kiln cools so fast it doesn't need to be propped
open until we're ready to empty it. Good luck finding out what stress
limits your pots can take! (you never know till you try!)
Cheers!
Tracy
Sarah Barnes on wed 5 nov 97
We fire fast here at school. The bisque kilns go off about 11 pm and I
unload at 8:30 am. I haven't had any problems handling the ware this way.
Also we fire ^6 gas and I open the door around 400 degrees. JUst a little
bit, unload the bisque takes about an hour or so and the gas kiln is
ready. Again no problems, as long as I wait for the kiln to be under 500
degrees.
I have on occasion pushed the kilns to the limit. I have been told this
does some damabe to the elements over the long term , but I do not know
for sure, but if I am in a really big hurry, after the electirc kiln has
shut off, I open the lid, use a brick to prop, then after the red heat is
gone open the lide the whole way, sounds scary but it works, I havent
lost anything, not even plates. I have only done this at workshops, I try
to be a little better organized at home.
Hope this helps
Sarah
in Baltimore
John Harlow on fri 7 nov 97
> For years I have been religious about opening my glaze firing no earlier than
> 90^ or less. Even then, I let the ware cool down to room temp. But when doing
> a large bisque firing ( getting ready for a show and wanting to push the
> limit) I am tempted to throw open the kiln lid at 300^ + and just let it
> speed cool. What is the possible limit and probable damage that I could
> incur? Thanks KEN
Opening over 500C and you might get dunting or first degree burns.
If you can stand the heat there should be no problems 200C - 300C.
If the clay cant stand that sort of thermal shock it's junk clay.
I have *always* unloaded bisqu @ 250C or thereabouts wearing heavy
gloves, never had time to waste waiting for room temp.
John
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