Convergent Series

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

Trying Art Clay Copper (Post #5 of ?)

Posted by C Scheftic on 2011/03/11

All my pieces have been fired and … sigh … it’s time to talk about firescale!

The first photo here shows the items in my second firing: taken from the kiln, quenched, removed from the quench bowl, and then knocked on the table a bit to see if any more firescale would fall off. Some did, but a lot remains. The darker-red colors in some of the pieces is what most of them looked like at that point. I tried using a steel brush on a few to see if it would remove any more firescale. Though that polished some of the darker red down to a lighter and slightly brighter copper color, it seemed to have no effect on the black bits. I was worried I might be burnishing them into the pieces, so I didn’t do much of that.

The six small pieces, from my first firing, were treated the same way, except I didn’t use the steel brush on them. Here, I did what was on the instructions, and moved them straight from the quench bowl into my pickle pot.

Now the instructions say they may need to be pickled for a few minutes. How many? Well, in part, that will depend on what sort of acid you use, and mine isn’t one of the strongest ones. I use, instead, one that’s based on citric acid: it’s still pretty harsh as far as acids go, but it doesn’t have as many nasty side-effects to people or the environment in general as some of the others. I know that, using it, I have to leave pieces in a bit longer than with, say, a sulphuric acid one. But, ummm, this is what the pieces looked like after two whole hours in the pickle, and then a good rinsing. You can see that some of the firescale is still flaking off, but there’s still plenty left…

2 Responses to “Trying Art Clay Copper (Post #5 of ?)”

  1. JeanT said

    I’m struggling with this, too. I did read that getting the firescale might take as much as 30 minutes and to keep pickling until there’s no more red. So, I pulled the pieces out after 10 minutes, rinsed, put in baking soda, brushed with a brass brush and repeated until there was no more firescale. I can’t pretend to be an expert on this, but it worked for me although the pieces turned out rather thinner than I expected.


    • C Scheftic said

      Thanks for the note, Jean.

      You’re commenting several months after I posted this and, I suspect, as a result of finding this particular post (and maybe a few others of mine) via a web search. Have you read all 10 of my items from March 2011 on my Art Clay Copper saga? Or any of the other ones about how much I like working with Hadar Jacobson’s clays?

      I’m not convinced that paying a premium price for Art Clay Copper in order to fire it in the open air is the way to go. I was happy to try it to see if it would save me any hassle compared to the other brands that must be fired in carbon. But the results I had (plus what I’ve heard from some others, though not everyone) have left be doubtful. I’m still willing to be convinced otherwise by true experts with it, but I’m not there yet!

      From what I currently understand about copper (that is, as a very curious person who is still learning here), the open air firing, plus the resulting firescale and thinning, do not make for the strongest end result. Which is something that really does matter to me!

      One way around that concern, of course, is to treat Art Clay Copper like any of the other copper clays, and fire it in activated carbon. But if we’re going to do that, then there are other clay formulations to choose from. If you’ve not tried any of those yet, I’d suggest that you do so. Get a feel for several different ones and let me know how they work for you. As with all metal clays (different metals, different brands, etc.), there sure seems to be a lot of different reactions to / experiences with each of them!


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