Convergent Series

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

Snowy White versus Shiny Silver

Posted by C Scheftic on 2011/11/28

As I was polishing up a few pieces recently, I decided to take a “comparative” photograph that I could save and use when discussing a certain point in some of my workshops. (In my studio, I often have a few examples available, but sometimes I don’t think to pack them up when I teach at other sites…) And, while I was at it, post about it here too, for anyone curious about the topic.

Q: What topic? A: When you work with fine silver metal clay, and fire it (either with a torch or in a kiln), what’s the “white stuff” (or, sometimes even, “glittery white stuff”) you see on the piece?

The answer to that question is: it’s the silver! When the clay is fired, and the binder burns away, and the silver atoms move in closer and re-organize themselves, then they tend to form a crystal structure such that they are all lined up and the light reflects off them in all directions, giving a white appearance. Depending on exactly how they line up as they cool, it may be more of a white-white or a glittery-white, but it’s still white. (I’ve no idea if this is technically accurate but, in the mental model I have of this, I think of it as comparable to how snowflakes form. As in how, under different circumstances, it will end up heavy or fluffy, etc.) Metal artists then use one or more of a range of techniques for burnishing the silver, polishing it, forcing the crystal bits to lie down all in the same direction so the light reflecting off them has that normal, shiny, metallic color. (Other metal clays will produce a similar effect in their all-metal end-product. On a number of occasions already, I’ve posted about the range of colors one sometimes gets when firing copper and, especially, various bronzes. It also happens with gold and steel, though I don’t recall ever stopping to capture that in a photo … yet.)

In the shot near the top of this post, the bottom two pieces remain in that “kiln-white” color, while the top two have been polished to more of a silvery-metallic look. More polishing could get them even shinier, but I thought that was enough for those pieces, at least for the time being.

As for the snowy-white ones, they do have to be polished: That finish is not stable. Anything you do to it (from the lightest rubbing to bumping it and so on) will undo-that “white” look. It won’t necessarily make it all shiny, but it will turn that part so it’s more clearly a silver shade. So the safest thing is to just polish it from the start, to whatever extent seems most appropriate (to both your artistic vision and your technical skills; for example, one could polish the high points to a very shiny state, and leave the more-protected valleys with some of the white look).

I’ve just finished adding a patina to one of the polished pieces with some “liver of sulphur,” so I will close for now with a photo of that.

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