Tree Pendant, Mixed metal with Bronze, Copper and Brass. Sawn, Hammered, Riveted, Antiqued. Based on a post from Barbara Becker Simon, I tried several new firings of Metal Clay Adventures brand BronzClay. I have had decent success with firing the bronze clay in small stainless steel boxes (lunchbox style nesting boxes from The Container Store), coconut shell carbon, Full ramp to 1600 F, hold 3.5 hours. But sometimes random items would not sinter fully. Fortunately I was able to catch them before they were sent out to customers. Re-firing again for a second time solved the problem. Most of the time.
Barbara recommends firing base metal clays on an open shelf at Full Ramp, 1000F, hold 30 minutes and let cool. When cool, bury in the coconut shell carbon nest and fire as you normally do. (For me, this is the Full Ramp to 1600F, hold for 3.5 hours).
I have tried this method 3 times and it works PERFECTLY. The pieces are about 3 cards thick and though some are seriously warped after firing, annealing and hammering allows them to be flattened for riveting. I have had no cracks either after firing or after flattening. I generally drill holes before the firing.