exploding part

Well you all my get a chuckle out of this, I test fired my little kiln
Sunday with a test piece of work. I turned the thing on to full blast
and my part was reduced to little 1/4" pieces of ceramic when I opened
it up Live and learn, My instructor at school got a big laugh out of
it when I told him what I'd done. I said it only got up to 1500 deg and
it took about 8 hours to get that hot. So now I know, soak it at 200 deg
for a couple hours before going hotter. DOH!!!!
L8R, Bri.

was the piece wet or leathery hard? i've had that problem with work i have
fired for student. and even had it explode after soaking it for 2 hours at 200
degrees.


"Democracy is two wolves and a lamb voting on what to have for
lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759

"Bri" wrote in message
...
Well you all my get a chuckle out of this, I test fired my little kiln
Sunday with a test piece of work. I turned the thing on to full blast
and my part was reduced to little 1/4" pieces of ceramic when I opened
it up Live and learn, My instructor at school got a big laugh out of
it when I told him what I'd done. I said it only got up to 1500 deg and
it took about 8 hours to get that hot. So now I know, soak it at 200 deg
for a couple hours before going hotter. DOH!!!!
L8R, Bri.

The usual way to fire a bisque kiln is to raise the temp by 100C every hour
for the first six hours or until you reach 600C. Then you can go flat out
to bisque temp usually 1000C it is then best to soak for half an hour to
give all impurities time to burn out.
OK converting
100C = 212F
600C = 1112F
1000C = 1832F

Thanks, I'll try that process next time I fire the thing up. I'm doing
my cone 10 stuff at school now but I'll be doing low fire 04 stuff in
that kiln for a while.

annemarie wrote:

"Bri" wrote in message
...
Well you all my get a chuckle out of this, I test fired my little kiln
Sunday with a test piece of work. I turned the thing on to full blast
and my part was reduced to little 1/4" pieces of ceramic when I opened
it up Live and learn, My instructor at school got a big laugh out of
it when I told him what I'd done. I said it only got up to 1500 deg and
it took about 8 hours to get that hot. So now I know, soak it at 200 deg
for a couple hours before going hotter. DOH!!!!
L8R, Bri.

The usual way to fire a bisque kiln is to raise the temp by 100C every hour
for the first six hours or until you reach 600C. Then you can go flat out
to bisque temp usually 1000C it is then best to soak for half an hour to
give all impurities time to burn out.
OK converting
100C = 212F
600C = 1112F
1000C = 1832F

OK, I just put another peice in the kiln and truned it onto the lowest setting.
The part is harder than leather but still cool so it's not dry. I'll leave it on
low for 4 hours and then start going up. The kiln is an Olympic 129FL with the
infinint power switch so that should be less than 200f. I hope this time it works
without blowing up.
Oh yeah, I'm the same person as "bri" but on a different computer.


MKent41616 wrote:

was the piece wet or leathery hard? i've had that problem with work i have
fired for student. and even had it explode after soaking it for 2 hours at 200
degrees.

"Democracy is two wolves and a lamb voting on what to have for
lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759

Bri:
Water boils at sea level at 212F. You will not be removing the moisture
from the clay at less than that,
assuming you are at sea level, higher if your elevation is higher.
my suggestion would be to give it 200 for an hour, then go to 300 for at
_least_ an hour or two,
to remove the maximun amount of moisture, then ramp up from there to cone 06
to bisque the piece.
You should be using some sort of temperature sensing device like a
pyrometer to determine the exact temp that is achieved.
Hope that helps,
Wayne in KW

"Bri" wrote in message
k.net...
OK, I just put another peice in the kiln and truned it onto the lowest
setting.
The part is harder than leather but still cool so it's not dry. I'll leave
it on
low for 4 hours and then start going up. The kiln is an Olympic 129FL with
the
infinint power switch so that should be less than 200f. I hope this time
it works
without blowing up.
Oh yeah, I'm the same person as "bri" but on a different computer.


MKent41616 wrote:

was the piece wet or leathery hard? i've had that problem with work i
have
fired for student. and even had it explode after soaking it for 2 hours
at 200
degrees.

"Democracy is two wolves and a lamb voting on what to have for
lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759

It's not just the free water in the clay which has to be released in the
bisque, there is a lot more to it than that. There is water as part of the
molecular formula of clay which has to freed from its molecular bonding,
there is organic materials (carbon, sulphur) which has to be burned out,
then there is the conversion of the silica from alpha to beta at about 573
degrees C, and more! This is why sometimes kilns seem to "stick" just before
the pots reach red heat - there is a massive additional heat requirement to
release all the inorganics and convert the silica.

The short answer is that the ramp rate for a bisque should be kept below
75 - 125 degrees C (depending on how solid the pieces are) until the pots
start to show colour, or about 600 deg C. Then you can be sure that all the
water and organics have gone, and the ramp rate can be cranked up without
risk of explosion.

Dave

--

Bri:
Water boils at sea level at 212F. You will not be removing the
moisture from the clay at less than that,

degrees.

I don't think this is quite right. If you initially ramp your kiln to
about
950c and soak for an hour for an hour or so dry the moisture out of the
clay so that when the temperature rises over boiling point the free water
has gone. Its the boiling of the water and the steam produced which blows
the piece apart.

This is why grogged clay takes rougher treatment as there is plenty of
outlets for the steam.

Cheers AJ

MKent41616 wrote:
was the piece wet or leathery hard? i've had that problem with work
i have fired for student. and even had it explode after soaking it
for 2 hours at 200 degrees.


"Democracy is two wolves and a lamb voting on what to have for
lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759

To persist in using some-one else's quote for a sig shows a lack of original
thinking on your part

--
Robert B* II

To persist in using some-one else's quote for a sig shows a lack of original
thinking on your part

--
Robert B* II


I'll take it to email if you will



"Democracy is two wolves and a lamb voting on what to have for
lunch. Liberty is a well-armed lamb contesting the vote."

-- Benjamin Franklin, 1759