Convergent Series

learning, using & teaching metal clay, and other aspects of life

While waiting for something to happen…

Posted by C Scheftic on 2011/03/28

Having finished, for the moment at least, my tales of my trials with Art Clay Copper, I figured I’d me mention something else I’ve been exploring at the same time.

One of the things about working with metal clay that really can suck you into it is this: There are a lot of times when you’re sitting there for a little while, waiting for something to happen (a component or a connection to dry out, some clay to rehydrate, some pieces to fire or tumble or react to a patina solution, whatever). It’s often not a really long time, but in some situations it is long enough that it’d be a shame to waste the time doing nothing. And, with all your metal clay and tools and everything sitting around, what better than to start work on a new piece?

So, while I was playing with copper clay, I was also playing with using copper sheet combined with silver clay. (I may eventually use both copper clay and silver clay to produce a single piece, but figured I’d reduce a few variables by first trying the regular sheet form of copper with silver clay.)

In the past, when I’ve mixed metal clay and copper sheet, I’ve combined them–after firing the clay to just metal–with any of a number of cold connection techniques. This time, however, I fired the silver clay right around the copper component. I started with some solid copper sheet that had been stamped out into a large “washer” size. I formed a bit of silver clay around it, and fired the two together. Now, the silver clay shrinks as it fires, which I think of as having the silver “hug” the copper.

This piece was fired at the optimum silver clay temperature of 1650. (Depending on the brand, copper clays may be fired somewhere between 1500 and 1800°F; the melting point of pure copper is 1984° F.) That 1650 temperature is, of course, well hot enough for various copper oxides to form on the copper.

As soon as this piece had fired, while it was still hot, I removed it quickly from the kiln (watching its red glow darken to black in the seconds it took me to move it) and quenched it in lukewarm water. A bit of firescale popped off from around the edge of the piece, but most of it remained on the two larger copper faces.

In one of her books, Hadar Jacobson mentioned that you could take a piece from the kiln, reheat it to a red glow, requench it, and the black should “peel of easily.” Now it wasn’t clear to me why I should have to reheat it if I’d done a quick-quench the first time, but I gave it a try. A little more black popped off from around the edge, but there was no peeling possible (let alone easily!) of the stuff on either face of this copper washer.

So I tried something else, suggested as one other alternative by Mary Hettsmansperger: brushing a just-cooled piece with a brass brush! That produces the interesting effect of turning the black coating to a sort of brassy-green color. It seems like that is stuck on: it still won’t come off at all easily. It does, however, tend to chip a bit at the edge, producing small brassy-black chips. I’ll have to wear it around a bit to test if that will eventually stop, or become more pronounced, or what. I’ll report my findings back here … eventually.

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