960: A new alloy of sterling PMC

Book made with 960 sterling

For the past year I’ve been working with an enriched version of sterling metal clay. "Enriched" simply means that this alloy has more fine, or pure, silver in it. It's still sterling, and can be legally marked as such.  We're calling it "960". That number refers to the amount of fine silver in the alloy just as 925 identifies regular sterling.  

960 is made by mixing equal parts of PMC Sterling and PMC3. I open a 25 gram pack of PMC3 and a 25 gram pack of PMC Sterling and mix them together. It takes less than 5 minutes. It's really that easy. 

You mix it, kneed it, fold it and so forth until it's uniformly colored.  No water, or oil is necessary when mixing these clays.

This is simple to do because PMC Sterling is a grayish color and PMC3 is more beige. Probably because I've done a lot of cooking in my life, once it’s uniformly colored, I let the mixed clay rest for 1/2 an hour or so.  Enclose it in plastic, the way you would with any other metal clay.

I just taught the first class using this new material.  In the class, at The North Country Studio Workshop conference at Bennington College, the students made their own 960 to work with. It got great reviews.

From left to right: PMC Sterling, 960. PMC3

Although I love the way PMC Sterling handles, it does have a couple of drawbacks, or one major drawback, really; the carbon firing.  Carbon firing is just not fun.  No one likes it and I think it's holding PMC Sterling back from the attention it deserves. It's so much stronger than fine silver PMC, has a longer open working time and superior dry working qualities. But then, you have to fire it, twice, and there's the carbon!

960 is almost as strong (in my opinion), handles almost as well, carves almost as well as 925 PMC Sterling but NO CARBON!  It fires in air on a kiln shelf like any of the fine silver PMCs.  We've been firing 960 at 1500F for one hour.

It has another perk; gold foil, when you keum-boo, goes on more readily than it does on PMC Sterling.  However, it doesn’t diffuse into the silver surface as quickly as it does with fine silver (I guess that’s really two perks).

Is there a reason to continue to have PMC Sterling in my studio?  Yes, PMC Sterling is peerless for that occasional very delicate design that requires extra strength.   It's also, in my opinion, the best way to fire diamonds in metal clay.  Although diamonds will survive an air-fire, the temperature must be quite low or they will not survive.   I like to fire my metal clay as hot as possible so if I want diamonds in a design I will use the original PMC Sterling and I’ll fire in carbon.

How did 960 come about? A year and a half ago I met with Tim McCreight and a few others to discuss PMC Sterling.  On the last day of the meeting we were brainstorming and Tim said, "What if we enriched the PMC Sterling?  By increasing the fine silver content of the alloy maybe we could get rid of the carbon altogether.”

The idea had an immediate effect on me.  It resonated; I went right home and mixed up my first batch of 960 and that's really the only metal clay I've used since then.

Please try it for yourself and let me know how it goes!

Pieces made with 960:

When it's fired and finished, I'll rivet something between the window and the little frame and cover the blank pages with decorative paper.  In air, the pencil burns off.

At this point, after so many 960 pieces, I trust this clay to sinter without distortion, in air, on a kiln shelf.  I'll fire this book soon, but not assembled.  Each page will be laid on the shelf.