Friday, June 26, 2009

Working with CopprClay - firing

I was very pleasantly surprised by how easy CopprClay is to work with. After receiving some packages from Rio Grande to test out, I found it hard to stop! The clay feels very good, and I found it much more user-friendly than the silver clay that I've worked with before.

A little olive oil to keep it from sticking to your hands or to the molds that you use, and you're pretty much set. Keep it well-wrapped when you're not using it. I cleaned out a small bottle to use as a slip jar, and little dried out bits (including filings) go in there. I used the slip to paint over then sea shells and to repair cracks in other pieces.

The clay must be completely dry before firing, and unlike silver clay, it doesn't seem to dry out all on its own. I put all the pieces on a sheet of parchment paper, and stuck them in my oven at 200 F for about 20 minutes. If they go into the kiln wet, you run the risk of blisters and cracking.

Firing the clay is a bit more work than silver. Copper and Bronze must both be kept from too much oxidation or you'll just end up with a black burnt-looking surface. Therefore, these clays must be kiln fired in a pan of charcoal. I used the recommended coconut shell-based granulated activated charcoal and a steel firing pan. (All tools can be found on Rio Grande's website.)

In the picture above, they are sitting on about an inch of charcoal, which will then be covered almost to the top with more charcoal. The pieces need to be spaced out, but you can add more layers of pieces if you keep them properly spaced.

I fired my first set of pieces all in one run, ramping up my kiln to 1700 F and holding for 3 hours. I didn't use any special schedule for ramping up, and actually the temperature ended up going a bit too high on the first go, but it didn't seem to affect the pieces except maybe the key. I was afraid that when I opened the kiln I'd find melted puddles in the firing box!

There were two pieces that didn't turn out quite as I was hoping: the shaft of the key ended up bending, which may have been because of the excessive heat, and the shell that I treated with blue enamel looked crusty and burned. When I brushed it off, it looked more like BronzClay than copper!

My next step will be to experiment with some different finishing techniques. I'm going to use a brass brush, and then burnish and buff these pieces. Maybe a few of them will go into the experiment pile for patination.

Copyright 2009 Cyndi Lavin. Not to be reprinted, resold, or redistributed for profit. May be printed out for personal use or distributed electronically provided that entire file, including this notice, remains intact.

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Tammy said...

Even bent a little, I think the key looks great. It looks antique.

Cyndi L said...

I'm going to add a verdigris finish to it, Tammy. Then it will look REALLY antique :-)

Christine Ritchey said...

I love how every piece turned out! Tammy's right about the key - it looks like an authentic antique key.

Please keep sharing your experiments with your adoring public! *-> I'm just starting to play with these clays and I can use all the help I can get!

Cyndi L said...

LOL! Thanks Christine :-)

The clay is so addictive, and since it's so much more affordable than the silver or gold, I feel more free to mess around a bit!

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