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.

Reply to
Bri
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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

Reply to
MKent41616

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
Reply to
annemarie

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:

Reply to
Bri

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

Reply to
psci_kw

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

Reply to
David Coggins

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

-- Robert B* II

Reply to
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

Reply to
MKent41616

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