My next class is on October 29, when we’ll make a pair of earrings using FASTfire BRONZclay and a selection of beads from Lisa’s Two Loose Beads shop. To my eye I have an unnervingly huge selection of beads, so I had to narrow down those choices and put together a rustic, end-of-summer theme. The pieces are fired as seen below, and to the right is a pre-fire pair Lisa made that’ll be fired early next week. So cute, so rustic. I love the color of this fired clay and have little desire to do much else for this project except to burnish on the petals. It will polish to a shine, a light gold that can look more like rose gold than yellow.
FASTFire bronze has been around for several years but this is our first go at it. Fast? That is as perfect as it can get for a metal clay class, but online I found more than one firing schedule. Some of them differed from the package-claimed 2-hour schedule, so there was some investigating to do.
How did these firing schedules differ from those on the package? One noticeable factor was that the temperatures being used by others remained the same (1525F) while the firing times changed. Some firings went up to 4 hours, double time! That wasn’t a fast fire in my mind, so I hunched that there was a way to do it in 2 hours…I decided to start from scratch and follow the package instructions.
The result was as follows using my Paragon SC2 kiln: Two test strips of different thickness were fired to this schedule: ramp temperature at a rate of 1525F degrees/hour (that took an hour) and once at 1525F, hold for an hour. That’s your 2-hour firing. Well, both strips broke. I tried again, keeping all the same except the hold was now for not 1 but 2 hours. This was a common schedule I ran across, but this piece also broke. I was feeling slumpy, but knew I had to find my own answer.
Reviewing my stacks, I found a flyer from Rio that stated the temperature could be raised anywhere from 50-100 degrees. 50? 100? That seemed a lot, but it also seemed my pieces were not getting hot enough to sinter! I upped the hold temp to the max, +100 degrees to 1625F. If this worked, the 2-hour firing claim might be reached.
Eureka! The SC-2 did its thing and fired the new test strip perfectly in 2 hours. I was even able to bend the piece back from the mandatory 90-degree bend. Happiness! Because there was some odd bubbling on the back, I decided to lower the temp to 1600 degrees (a 75 degree difference from the original instructions) but it broke. Maybe somewhere in the 25-degree difference lies the lowest sinter temp, but I’m done with test strips for FastFIRE!
The remaining conclusion for this topic is that kilns obviously fire differently. Lisa has the same kiln as I do, so when she fires her strip we will see if my schedule also works on hers. It should, unless the temp monitoring is faulty. Our kilns both fire silver clay flawlessly, though, so I doubt it.