Firing Disaster Continues
Still not having much luck with the firing. As a recap, I planned to refire a number of pieces of bronze clay which were under-fired first time around. In the same tub I included two copper clay “bags”.
This is the schedule I used.
- Ramp: 253 F per hour (137 C)
- Target (Hold) Temperature: 1530 F (830 C)
- Hold 3 hours.
All the copper crumbled.
Rio Grande’s recommended firing schedule is as follows:
COPPRclay™ Firing Schedule (for pieces that will not be enamelled):
Regardless of thickness (embedded in coconut shell-based activated carbon): Ramp at full speed to 1700°F-1800°F (927°C-982°C) and hold for 3 hours (total firing time, including ramp-time, will be about 4 hours). Most firings perform well at 1700°F. However, if you discover that your pieces are not sintering properly, try firing them at 1800°F. Please Note: Blistering may occur at 1800°F; if this occurs, slightly decrease the firing temperature.
If I went by this I would say the problem was obvious. The kiln was not hot enough but I was used Hadar’s original copper clay not COPPRclay. Hadar’s schedule is as follows:
It is bit more complicated but not as hot. Perhaps missing the first phase was the problem.I have not yet had any success with copper clay although I have only tried Hadar’s original clay. I have a package of CopprClay lying around so I may try that next.
I wasn’t really expecting the bricks to fire properly. As you can see, I wasn’t disappointed;)
There was one success. I repaired the broken bail on the landscape pendant. It came out of the kiln with a nice patina but it wasn’t quite what a wanted. After a bit of sanding and tumbling it came up more how I wanted it to look.
A added some blue resin in the hole as enamelling sounded all too hard. I’ll call it “Blue Moon” after last weekend’s Canberra moon.
I found a firing schedule in Metal Clay Arts Magazine that has been working great for copper clay. I make my own clay, but it seems to behave the same as Hadar’s Copper Clay.
First firing, not in carbon. I lay them on a 6″ square white glazed wall tile (78 cents at Home Depot) instead of a kiln shelf.
Ramp 250F/Hr to 560F Hold for 45 minutes
This first firing gets rid of the binder. I found the pieces are durable enough to transfer into the carbon without any problems, but I’d still try to be gentle.
Second firing in coconut carbon in the stainless steel pan with the lid on.
Ramp to 1750F Hold for 3 hours (they say as fast as possible, I got
shinier copper when I ramped at 850F/Hr)
The pieces will come out pink/tan with a matte powdery finish. I tumble pieces in steel shot for about an hour and they’re like new pennies.