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Tuesday, May 12, 2009

Firing Metal Clay, Bronze versus Copper


Well…. An interesting turn of events.

I fired copper and bronze together (not pieces that were copper and bronze together, but copper pieces and bronze pieces… see the pic from my last blog entry).

When I began sanding the first piece (just happened to be a copper hollow bead), there was a spot on the top and side that wouldn't sand… it just remained black.

Anyway, I went on to sand my identical beads in bronze, and although they're pitted and a smidge concave, they at least seem to be fully sintered.

Then I picked up the next piece, a copper tube bead. And same thing… there was a black bit that wouldn't sand. But just before I removed the dremel, that part of the bead collapsed (disintegrated).

This made me wonder... does copper need a slightly different firing schedule (for my kiln, anyway) than does bronze?

As you can see by the rest of the pieces, the bronze seemed to fair just fine.

BTW, the one in the middle row on the far right IS copper, but it's very thin. And if you're wondering what it is… ha ha ha… I don't blame you.

When I was at Hadar's penultimate class, I was killing time while waiting for my project to dry so I decided to make a copper bead cap. Since I wasn't overly fond of how my bead caps were coming out when I molded them onto round objects to dry, I had the brilliant idea to make flat bead caps and just hammer them into curved shapes after the firing. Heh… Hadar informed me that baked metal clay isn't as sturdy as metal-metal so hammering after baking should be used to fix slight imperfections rather than for complete shape alterations.

So yeah, now I have a flat bead with a hold in the middle.

In the next photo, you can see how the bronze hollows went a bit concave on me.

And when I looked at these three beads lined up for my photo, something struck me as wrong. Then I realized what it was. These pieces were all made from the same pattern, so were identical in size in their green state. I'd completely forgotten that copper doesn't shrink as much as bronze so I forgot that the copper beads wouldn't end up the same size as the identical bronze beads I made them to go with.

Now in the next photo, you can really see the pitting.

I see I have a lot more work ahead of me than just figuring out how to make things out of clay.

I put my beads into the firing square (still don't know what to call it) vertically.

Hadar asked if I'd put charcoal into the hollow beads. I hadn't. The holes were small and I couldn't get it in. But maybe I should have tried harder and at least got a few small pieces in.

Interestingly enough, lots of charcoal WAS inside the beads because when I began sanding it all started jumping out. (That's the black stuff you see in the background of all these photos.)

I'll go back to Hadar's for class Friday, but I'm curious to know if I should try upping the temp or increasing the hold time.

I'll keep you posted.


Yes, many of you know Monica as my lovely hand model.

Anyway, she managed to slam her hand in a car door and I took her to the doctor. One broken finger.


Two very intense NHL play-off hockey games last night.

Oh, speaking of hockey, remember that blog post from a few days back about having faith in your hockey teammates? Well, on Saturday, Gabe's team was losing zero to three and they came back with five unanswered goals to win that quarter-final game.

During the semi-final the next day, they had a one-zero lead over the undefeated Padres all the way until the last five minutes. Unfortunately they didn't come out on top, but losing one to two tells me it really could have gone either way. Good job boys!


Alex: eBay fees have gotten out of hand...they're not working for me either. I pay them more, and am getting less for my beads...and sadly they're still the biggest dog in the neighbourhood or I'd go elsewhere....

Sorry to hear eBay's not longer good for you either. And yet, they ARE still the biggest dog in the neighborhood. Gggrrrrrr!!!


  1. firing square---maybe the word sink would work?

    thanks again for sharing your process. there are just so many variables with this clay stuff.

  2. Greetings,

    This is a question for the webmaster/admin here at laurabrackenblog.blogspot.com.

    May I use some of the information from your blog post above if I provide a link back to your site?