Use of PMC3 and effects on kiln -

Use of PMC3 and effects on kiln

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Use of PMC3 and effects on kiln

Postby Ernsglass » Sat Jan 24, 2004 8:26 pm

I am interested in using some PMC3 (Precious Metal Clay) to encase some cabs, but have read various places that it may have a effect on your kiln, leaving deposits, effecting heating coils, etc. Would be interested if anyone can comment on the effects, would it be wise to use shelf paper or fire directly on the shelf? Do you need to prop the lid to vent or not? Most of the books on PMC and ArtClay do NOT mention this, but I am hoping that I can get some comments from those with experience. Thanks in advance for your help. Ernie

Stuart Clayman
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Postby Stuart Clayman » Sun Jan 25, 2004 2:16 pm

I have gotten different answers when I talked to different manufactures about it.
I was at an Open House for a distributor and someone selling PMC and also a fiber kiln were there. The person said that the kiln was designed by the same person that designed the SC2 from Paragon. (The person left Paragon and went to this company). I asked if I could use their PMC in my existing kiln with coils and he said no, that it left deposits ect. I said thank you and then said that it was disappointing cause it would have been nice to do both in the same kiln. He did not stop me and try and make a PMC sale.
I then talked to the president of Paragon and asked him the same questions and he said that he knows of no problem with it and knows of people that use PMC and glass in the same kilns with elements.
I have kept asking others the same quesiton and I have found that there are peple doing it with no problems (as of yet).
I am going to let people use it more then see what the answer is.

Good luck,

Judi R
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Postby Judi R » Sun Jan 25, 2004 2:22 pm

I have used PMC and ACS with glass in my kilns, and have not experienced any problems. I do use shelf paper but I'm not sure you would have to. No deposits or residue.

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Postby TerriG » Tue Jan 27, 2004 6:23 pm

I have fired multiple times with PMC over the last year in my glass kiln with no after affects. You can see the outline of the piece on the shelf after the firing but that hasn't not caused any issues as yet with subsequent glass firings.

Barbara Muth
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Postby Barbara Muth » Tue Jan 27, 2004 6:31 pm

I frequently fire silver in the kiln in the form of uncapped leaf and foil. Not the same as PMC, I know. I can't report on residues on the elements but I can say with confidence that when silver stains (or not) my shelf, if I fire glass on that part of the shelf that usually reacts with silver, it reacts with the silver left behind on the shelf.

Check out the glass manufacturer's recommended firing schedules...

Linda Hassur
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Postby Linda Hassur » Tue Jan 27, 2004 8:41 pm

I was having problems with black spots on some BE glass. I sent them a sample to help me solve the problem. They said that it was caused by silver. I had never fired silver in my kiln but do metalworking adjacent to the kiln. I never did figure out how the metal got onto the glass but I don't think I'll fire PMC in my kiln for that reason.

Judi R
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Location: San Carlos, CA

Postby Judi R » Wed Jan 28, 2004 2:36 pm

I took a class on PMC and here's what I learned:

Regular sterling silver is .925 pure with (I think) nickel constituting the balance, and that's what causes black spots or discoloration on glass. PMC Clay is .999 pure. I've accidentally used both in my kiln (oops :evil: ) and the sterling does cause a problem that the PMC does not with regard to discoloration.

I've tried several projects using PMC clay and glass. Only the lower-fire temp PMC clay will work. Nevertheless, the shrinkage rate of about 10% makes it difficult to encircle or surround glass with PMC clay; you get gaps or breaks in the silver where the silver shrank and the glass did not.

In order to get a good shine, you have to buff the silver after firing. If you use PMC on top of a glass piece, the clay burns off on the top but does not burn off sufficiently on the bottom, and you can't buff there; so if the glass is clear or light colored, you will have slight discoloration underneath the silver which may show through.

Another problem with PMC is that it fires to the same shape as you put it in ... i.e., it doesn't melt down or get smoother in the process. If it's not perfectly formed and smoothed before firing, you will have to coldwork it and sand or grind the silver. Depending on whether it is atop the glass or adjacent to it, the grinding will impact the glass.

I haven't yet been satisfied with the results of my PMC / glass work :( , but I keep trying because it sure seems like it could be cool. Anybody have ideas?

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Postby artisand » Thu Jan 29, 2004 11:25 pm

There is another thread running titled "Any Kind PMC and Glass" in which "Candy" has offered to answer any questions about PMC and glass. She has several years of experience.


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