Friday, November 30, 2012

Does PMC Sterling Silver Clay React to Aluminum?

by Janet Alexander
Technical Advisor

Jamie Sells wanted to know if the new PMC Sterling Silver metal clay reacts to aluminum like the fine silver metal clay. 

Over the years I’ve been told not to place my metal clay on aluminum or there would be a reaction, so I never have. With that being said, I don’t know what the reaction is! Inquiring minds want to know now! So, I tested PMC3 and the new Sterling Silver metal clay to find out.

I placed a sample of each clay type, PMC3 and PMC Sterling, on aluminum foil and also samples on an aluminum pan. I cut out a total of four oval discs labeling the discs that are laid on top of foil with an " F" and those laid on top of the pan with a" P". I allowed them to sit there for an hour, until they were fairly dry.

PMC3 on the right and PMC Sterling on left.

PMC3 on the right and PMC Sterling on the left.

The two samples on the foil had a huge reaction as did the foil.

Reactions to the foil.

The foil's reaction.

The two samples on the pan had a less of a reaction to the aluminum.

PMC3 on the left and PMC Sterling on the right.

It looks like the combination of moisture, clay, and aluminum causes the reaction. The PMC3 clay on the pan had less moisture and so had little-to-no reaction whereas, the foil seemed to trap the moisture between the clay and foil.

I fired each sample per the manufacturer’s directions to see if the reaction area would burn off. It did not. The areas that reacted with the aluminum are raised an bumpy. It gives the clay a look of reticulated metal.

Polished metal with reactions to aluminum foil.

Polished sterling silver exposed to aluminum pan.
 So, if you want a cool looking texture, now you know how to get it. Otherwise, keep the clay away from aluminum.


Lora Hart said...

A student once dropped off some work to be fired that looked just perfect in it's dry and ready for the kiln form. The second half of this post shows what I found when I opened the kiln door! Silver metal clay and aluminum just don't play well together!

Drakonaria said...

Wow, this is very interesting. I had no idea that such reaction occurs!

mfglaeser said...

I have the bare aluminum ring mandrels (early ones before they anodized them), first ring I ever did I used this with nothing to isolate the PMC from the aluminum. Mine looked fine, didn't have that reaction. But...after firing they were brittle, they hadn't distorted like Lora's, but after hitting on a mandrel, it was clear they were like Swiss cheese. I have worked with covers on the mandrel since. Thanks for posting the tests with sterling!!

Janet Alexander said...

Thanks Lora and mfglaeser. So to put it differently, just because you can't see it on the dry clay, doesn't mean it hasn't reacted!