PMC firing times

Jewelry Discussion
1

I wish to clarify my previous post, as I have been corrected off
line. I listed my two preferred firing schedules for PMC+, not all
the possible ones.

Your choices for PMC, officially, off the package, are:

1650 for 10 minutes
1560 for 20 minutes
1470 for 30 minutes

My preferred firing times are:

1470 for 30 minutes (in workshops, where time is an issue)
1650 for two hours (in the studio, when there’s plenty of time)

At 1650 for two hours, you get a 5% increase in density. And, it
takes a long time for the kiln to get up to 1650, it doesn’t save
time that the firing time is only 10 minutes. If you’re going to
take the time to get the kiln heated up that high, then you may as
well leave it in. My kiln, the Paragon SC2, takes about an hour to
heat up to 1650. I can do the full ramp up and hold time for 1470
in an hour.

So there ya go. Let’s not even get into PMC Standard or PMC3.

Elaine
Elaine Luther
Metalsmith, Certified PMC Instructor
http://www.CreativeTextureTools.com ™
Hard to Find Tools for Metal Clay

2 
At 1650 for two hours, you get a 5% increase in density.  And, it
takes a long time for the kiln to get up to 1650,

But, I see no one mentioning how much more shrinkage there is at
1650 for 2 hours (pmc+, and pmc3) If it becomes MORE dense, it has
to shirnk more too.

3

Yep, that’s true, it will shrink more if you fire it at 1650 for 2
hours. This hasn’t been a problem for me.

Elaine

Elaine Luther
Metalsmith, Certified PMC Instructor
http://www.CreativeTextureTools.com ™
Hard to Find Tools for Metal Clay

4 
Yep, that's true, it will shrink more if you fire it at 1650

Any hints on “how much more?” Closer to 30%?

5

PMC Standard and Gold both shrink 30% since they are fired at the
maximum times and temperatures for each medium.

PMC+ and 3 shrink 10-12% depending on the schedule you choose. When
fired at 1650 for two hours they reach maximum shrinkage of 12%, if
you have rehydrated and added water to the clay, it may shrink a tiny
bit more, but no where near 30%

The times and temps suggested by the manufacturer of Precious Metal
Clay are as follows:

PMC Gold - 1830 for two hours
PMC Standard - 1650 for two hours
PMC+ - 1650 for 10 mins OR
1560 for 20 mins OR
1470 for 30 mins
PMC3 - 1290 for 10 mins OR
1200 for 20 mins OR
1110 for 30 mins

Art Clay Silver shrinks 8-10% and has a different firing schedule.
They never developed a material that shrinks 30%.

HTH,
Lora Hart