PMC problems

[Suzedablooze]

Hi,

another quick question because you lot are really helpful.

I have made a few things from PMC but I seem to have a problem with the finished object having edges breaking off. For example, I made a Gingko Bilbao leaf from a mould. I tried twice and both times the very edge broke off (different edges too otherwise I'd think it was something to do with that particular section).

Any ideas why this may be happening - is it that the clay is too dry when I place it into the mould?

Could it be the firing technique (I ramp up the teperature to about 1000 C then cool down to 650 ish before putting the clay in the kiln)?

Thanks in advance for any help - I've given up on PMC for now as its ending up as a lot of expensive mistakes.

Suze

[lorraineflee]

Hi
I always put my dried clay items into a cold kiln and then bring it up to temperature (650 say), hold for the required amount of time for the particular clay and let it cool down to room temperature before taking the items out. I've never had any problems with breakages with this method.
Lorraine

[MuranoSilver]

Hi Suze
Put your clay into a cold kiln and ramp up with the clay inside. Providing it doesn't have inclusions such as glass, or natural gemstones you can then fire at 800 to 860 for approx 20 mins (or longer).
I fire at 850 for 1/2 hour or an hour if it has rings in the batch.
If you're using the instructions that come with the clay, you'll find that this will result in a much stronger denser end result.

There's lots of PMC info on my PMC Tips blog (link in my signature) or just throw any questions up here. Lots of PMC folks here to answer them for you ;)
Nic x