Convergent Series

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

Silver Metal Clay “leftovers” — Mixing & Matching

Posted by C Scheftic on 2011/09/12

In my last post, I described some little elements I’ll make at the end of a session when I have only a little bit of clay left over. But there are times (I’m sure you have these too!) when I’ll be at the end of a session and just not have much time left to fiddle with the leftover bits. In that case, if what’s left is just a small amount, I may mix it in with some other opened clay. The important thing is to remember to mark what I’ve done: that is, if I’ve mixed, say, PMC3 with PMC+, or PMC+ with Art Clay Low Fire, then I make a note of that.

Why is the note important? Well, in those examples, it’s because PMC3 and PMC+ have different minimum firing requirements, while PMC+ and Art Clay Low Fire have both that and different shrinkage rates. Each clay has its own specific characteristics but, at one point or another, I think I’ve mixed up leftover bits of just about every possible combination of silver clays!

Yes, there are a few exceptions: Leftover sheet or paper clays don’t mix in well, but they are essentially “dry” elements that I just stash for later use as-is. Art Clay’s Oil Paste is a special formulation with a specific purpose–as a bond between pure metal pieces (not clays)–so it shouldn’t be mixed in with other products. PMC Pro contains copper, and should not be mixed with the fine silver varieties. But I have no qualms about mixing together with abandon the various fine lump clays, regular paste, and unusable dribbles from syringe-clay.

Also, though I try to minimize the amount of sanding that I do on dried clay, there are still times when doing that really is necessary. I save up any “silver dust” as I go and then, at the end of my session, I spritz the whole thing with a little bit of water, knead everything together well (whether it’s just all “dust” or a mix of dust and lump clay), and let it sit to finish rehydrating until the next time I sit down to work. Easy! And economical!

And, yes, I’ve mixed clay-dust of one sort with moist-clay of another. Same thing if I work on a piece, let it dry, decide it has some major issue that I just don’t want to deal with. I do try to mix it back in with some other clay of the same kind but, if I don’t have any of that handy and open when I want to recycle it, I’ll mix it with what I do have. Makes life simpler!

[Aside: I hear about other artists who suddenly go on a binge and “reclaim” huge amounts of dried clay at once. I can’t imagine letting clay just sit around in the quantities I’ve heard reported (many, many ounces). Any clay I have on hand gets used up as quickly as I can find the time to get to it!!!]

The main tricks that I see are:

  • I really want to knead any mix well, to be sure both the silver particles and the binders from the different clays are thoroughly distributed (I find that my experience with making both pie crusts and bread has paid off here);
  • I have to fire according to the “strictest” clay in the mix (though, with fine silver, I usually just fire everything at 1650°F for two hours anyway); and
  • I have to remember the effect of mixing on shrinkage: if the two clays have different shrinkage rates, then the mix will shrink a sort of in-between amount (and, how close to one end or the other of the range between the two will depend on how much of each kind is in the mix).

Because of the last factor, I do take a bit of care with how I use mixed-clays. They are just fine for simple, stand-alone pieces. The round one in the photo shown with this post (which is domed, textured on both sides, with added embellishments on the concave (hidden here) side) could well have been made with a clay mix. For the oval one (which was made from two ovals, each textured on only one side, dried, re-moistened on their plain sides and “squidged” together, then embellished a little bit more), I deliberately chose a “pure” clay, fresh from the pack. I could have used a “mixed” clay for the individual pieces but, in that case I’d want to be sure I had enough so I could use the exact same clay for all the elements. Otherwise, I’d risk having one layer shrink more than the other, thus distorting the shape. With clay straight from the pack, I can be sure I can have enough that’s all the same. An alternative, which I have done but can’t find a photo of just now, is to build a little bit of distortion into your design, and use elements made from clays with different shrinkage to achieve that effect. That’s your choice!

If you are wondering how all this applies to “base metal” clays (such as copper, bronze, steel), for now I’ll just say that there are possibilities but it’s not quite as simple. I’ll probably write about that eventually, but I’ve got a lot of other things higher on my to-do list, so that may not happen for a while…. I my next post, however, I will mention the one and only time I never use a batch of silver mixed-clay, myself, even if I’m sure I have enough to complete the project. (Your choice, of course, may differ.)


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