Tuesday, January 21, 2014

More Bonzclay

I've been working with Bronzclay now since Thanksgiving.  The last pieces are going into the kiln today.  And if none of them have to be refired, I'll be finished with bronze for awhile.

The clay is so nice to work with that I ambitiously made a couple of larger pieces before I realized that bigger, thicker pieces need a different firing schedule. I found some iris pods in the backyard last fall and thought they would make a nice focal piece for a necklace. But the piece I lovingly created turned out to be 13mm thick in the center.

While there is a lot of information about firing this clay out there on the Web,  I decided to contact the manufacturer himself for advice.  Bill Struve was very helpful and patient with all my questions as we exchanged a few emails.

We decided that the slow ramp process Mardel Rein has devised, which takes into consideration the type of kiln, the thickness of the clay, and the target temperature, would be appropriate to try.  So after an initial open air firing phase, ramping at 500° to 650° and holding for 45 minutes, I covered it with carbon and fired at 115° per hour to a target of 1490° and held for 3 hours.  Yes, the piece was in the kiln all day.

One of the pods broke at the seams but otherwise the piece was intact.  It was an easy fix.  The second firing used the same first phase.  But then buried in carbon it was a full ramp to 1510° with another 3 hour hold.  Bill Struve had told me that the slow ramp on already fired items wasn't necessary.

Cleaned up and polished, this was the result.

So what did I learn?
While bronze clay is so much less expensive to purchase than fine silver and I feel compelled to create larger pieces, firing time can cancel out the savings, even when you have solar panels.  So it's not something I will do often.

I'm thinking about digging out my husband's dehydrator.  Some of my smaller/thinner pieces tended to crack or break but they always seemed to be pieces with more than 1 layer and cracks began in the layered area.  It's possible that even pieces that sit around for awhile are not fully dry in the center of the thickest part.  Pieces that sat for a week fired without problems.  Those that were only a couple days old were the ones that cracked.

The shrinkage rate of Bronzclay makes it difficult to create my openwork/filigree designs.  Even when my coils are thicker, they don't seem to stay together.  So I may go back to Goldie Bronze for those designs despite its more grainy finish.

As I stated in an earlier post, bezels need to be attached to already fired pieces and the entire work fired.
 again.  Second firings can be at full ramp to target temperature.

Any pieces with nooks and crannies should be fired in a wire mesh cage.  Because of the shrinkage rate of Bronzclay, this is particularly important.  Small bits of coconut carbon can cause cracks in the design or become embedded in it.

My kiln is a Paragon Firefly and the bonding agent in this clay just would not burn out using the manufacturer instructions.  I had better results using a first phase firing on a kiln shelf then burying the pieces for the second phase.  I do this with both thin and thicker pieces.

Wednesday, January 1, 2014

A New Year with a New Bronze

Happy New Year!!!

I've been away from my blog but not sitting idle. In my last post I talked about my firing issues with Bronzclay.  Since finding a firing schedule that works I've been hard at work testing the clay with my new designs.

I'd like to report that some things work and some don't.

These small pendants were quick and easy and fired nicely.  Only the pendant on the far left had to be fired a second time.  I found when layering or attaching elements water is not enough to keep them together in the kiln.  Most attachments need a loose mixture of clay and water covering the entire surface of the adhesion.  If there are any spaces the piece will begin to separate.

I like to add flowers and curly snakes to some of my pieces.  But sometimes the little particles of carbon that the bronze is immersed in get stuck in all the spaces my style provides.  Sometimes that just means digging these particles out  but occasionally they interfere with the shrinkage.  This bronze clay shrinks a lot, about 20%, so the carbon particles immersed in a design will cause it to crack.  To solve that problem I've purchased some stainless steel wire mesh to cover the delicate pieces and keep the carbon particles out.

This high rate of shrinkage also makes it impossible to embed a bezel setting for even a small stone.   Because the setting doesn't shrink it causes clay around it to crack.  Bezels need to be attached to fired clay and the whole piece fired a second time.

It's been a learning process but all in all I'm happy with the finished products that have survived the kiln.  My new inventory for 2014 has some new designs I hope people will like.  Bronzclay is a joy to work with and the finished product sands to a lovely shine that I protect with clear coat.

Here's a sneak peak at more of my new jewelry soon available at Jansjems--