Sunday, August 29, 2010

White bronze

Hadar Jacobson has created a series of powdered clays that just need to be mixed with water. The powder doesn't have a shelf life like the other clays do. It comes in copper, bronze, white bronze and steel.

I've worked with the original bronze and copper clays. Although I've not worked with Hadar's bronze and copper, I had the opportunity to feel the texture and see the workability of the clay. (Very nice.) As with the original formulas the firing of the clays are where things get tricky.

I have had the opportunity to work with the white bronze clay. It mixed up smoothy and was very nice to work with. Once again, the firing of the clay is something that has to be worked out since each kiln may reach varying temperatures and the clay does not have a very wide range of forgiveness.

The clay (like the the original bronze) is fired in coconut charcoal (although without a lid). We fired ours in the stainless steel container, on a raised shelf. There is one inch of charcoal under the pieces and two inches above the pieces. The pieces should be spaced about a half an inch apart and away from the front of the pan. (The side near the door of my SC2 could be cooler.)

We (my friend Carol and I) fired the pieces at a full ramp to 500 with no hold. Then we ramped the kiln at 400 per hour up to 1250, then held for three hours. All in all the firing time took about five hours. We left it cool in the kiln overnight. The directions suggested to raise or lower the temperature by ten degrees if needed, depending on the outcome of the firing.

All of our pieces appeared to be sintered. But, in the process of cleaning them, discovered that a couple of pieces near the door were not fully sintered. (So back to the kiln.)

Since this was my first try with the white bronze, I kept the pieces simple. (I did try a larger fold-over bail pendant that I didn't fire yet.) I thought the clay shrank 30% like the original versions so I made my pieces rather large. Instead, the white bronze shrinks less than 10%.

Unlike silver clay (or the bronze and copper that I've worked with before), cleaning the pieces requires the use of a motor tool. The cleaning process also wore down the coarse brush of the tool very quickly. I stopped after the initial cleaning. Maybe further polishing would produce different results.

So far, the white bronze clay is not exciting me. It is easy to mix into a smooth workable clay, but for me that's about the best thing. The firing is tricky and the amount of pieces that can be fired in one firing is very limited. The length of the firing time and the cleaning process required to finish the pieces is a deterrent for me. (I had such a black dust all over my workbench. Guess I prefer gray dust.)

Maybe it's because I stopped at the first step of cleaning, but the pieces remind me of a tin can.
They have an industrial look (and I lean toward organic.) The tin can color does work well with a variety of bead colors. (The sample pieces will be turned into earrings.)

As I've mentioned in earlier posts, the jury is still out on these base metal clays. (I need to do more before I pass final judgement. The first time at anything isn't always successful.)


MotherSquid said...

I believe your firing end temps are a tad low. I have always fired white bronze at end temps of 1275 to 1325. Also, I've had powdered bronzes & copper from Hadar Jacobson for 3 years that mix, work & fire just like new. I thought the point of powdered clay was the longer shelf life. Perhaps we've had different experiences with this product, but I really like being able to mix a fresh batch the day before I start a new project & working with the fresh clay. Best wishes & good luck with future projects!

Alice Walkowski said...

This post is almost four years old when the powdered clays first came out. I've actually not worked with the white bronze since and haven't fired my big piece yet. I have been working with the powdered copper and bronze clays and "love" both of them. And, yes our firing temperature may have been low. It was our first try. I'll have to try it again and maybe finally fire my bigger piece at the suggested temps. I too like mixing the clay to my desired consistency and I do think the shelf life is long. Thanks for your comments.