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Charley261
26-09-2012, 10:21 AM
Hiya everyone!

I was wondering if anyone could help with a few kiln issues I have:

I have just bought a new paragon sc2 and have just used it for the 1st time and a few of my pieces melted (I fired it at 900 for 2 hours), the pieces were at the top and round the edges so I know to try and put things nearer the centre next time (although some of the embeddable fine silver findings on pieces in the centre also melted). I'd really like to fire things at a lower temperature to reduce the risk of melting and I have heard that it is possible to get a just as strong end piece by firing for longer at a slightly lower temp?? does anyone know if this is true? and If so what the temp and times are?

Also some of my pieces have a crystalline appearance after they came out of the kiln, the majority of this was removed with the steel brush and the tumbler but I still have a slightly uneven crystally finish on some bits - any ideas what is causing this?

Thanks so much to you all for such a helpful source of info!!

Kind Regards,

Charlotte

Dennis
26-09-2012, 06:53 PM
Hi Charlote, I don't do PMC now, but I did have a brief flirtation with it when it first became available in about 1995. I spent hours perfecting some pieces but when I put them into a grotty kiln in the college I attended, they melted to a puddle. At the second try I reduced the temperature by 50° C and all was well.

My guess is that the granular effect on your other pieces was due to the fact that they briefly remained molten just under the surface when you took them out. Granulation is an effect sometimes produced on purpose as a form of decoration.

At the time I did it the recommended temperature was 800°C but here is a chart for you: http://www.silver-clay.com/firing.htm.

Dennis.

medusa
27-09-2012, 11:47 AM
I thought that PMC didn't actually become molten, but sintered?

Dennis
27-09-2012, 12:48 PM
I thought that PMC didn't actually become molten, but sintered?

You're right Liz. In my reply above I suggested that while some pieces had melted, others damn nearly did, so Charlotte needed to reduce her thermostat setting http://metals.about.com/library/bldef-Sintering.htm

Charley261
04-10-2012, 12:26 PM
Thanks Dennis, the website you gave a link to says 1290 F for 10 mins? I'm only a beginner metal clay user but that doesn't really seem hot or long enough, I bought my kiln as blow torching caused my jewellery brittle, so I really want to use the full potential of my kiln and get really strong pieces, I might try a tester piece at 50 deg less for 2 hours and see how that goes,
Thanks very much, Charlotte

Dennis
04-10-2012, 09:00 PM
As mentioned in my first reply, I am not really up to date on this, but I would do what you suggested. There are lots of people here who do clay, but I presume they are torch firing.

If after a second try you still have problems you could also consider asking the manufacturers of your kiln for a new thermostat. Regards, Dennis.