Hi bloglandia! I'm Cindy, and I'm a (base) metal clay addict. I have my firing system pretty well worked out these days. It wasn't always like this, though. I remember being very unsure about how to fire bronze and copper. I did a lot of homework, but it much of the information available seemed contradictory. Book learning could only take me so far - I had to test the methods myself!
Since base metal clays need to be fired in activated carbon, you need a container to hold the carbon in. But what kind is best? Many of you probably thought you'd never have to worry about this, since you work in silver. However, now that sterling silver clay is becoming popular, you very well might need a firing vessel!
I can't claim to be an expert, but I can share what I've learned from direct experience using all the popular firing vessels - ceramic, fiberboard, fiber blanket and stainless steel. Here are what I believe are the pros and cons of each. If you've had different experiences, please leave a comment below so we can all learn together!
Ceramic firing vessels
Pros - durable, available in variety of sizes, won't "contaminate" the kiln (more on this later), can be used with a lid or without, transmits heat well.
Cons - susceptible to thermal shock, relatively expensive.
Fiberboard firing vessels
Pros - won't "contaminate" the kiln (more on this later), can be used with a lid or without, transmits heat well. Thermal shock isn't a concern.
Cons - not as durable, deteriorates after a few firings. Last I checked, was only available in a pretty small size.
Fiber blanket firing vessels
(For this method, you pin a piece of fiber blanket together with steel t-pins to form a firing box.)
Pros - relatively inexpensive, transmits heat well.
Cons - difficult to find materials, requires construction, flimsy, can be difficult to get in/out of kiln, can't withstand the recommended firing schedules for all brands of clay (I had one disintegrate entirely after a single BRONZclay firing - but the pieces sintered just fine at least!)
Stainless steel firing vessels
Pros - durable, cheap, can be used on a camp stove or gas burner to burn out the clay binder.
Cons - relatively poor conductor of heat, might leave kiln dirty.
Here is where the issue of kiln "contamination" comes in. Some stainless steel containers (in my experience, all of the square steel firing boxes - which are actually restaurant food pans, if you want to source them cheaper! - and most stainless steel mixing bowls) will turn black during firing. Black flakes and dust fall off the pan/bowl into the kiln.
My kiln is right next to my Shop-Vac in the basement, so this isn't much of a concern for me. Five seconds of vacuuming and the dust is gone. I put contamination in quotes because the dust is just that - dust. It is easy to clean up and is not ruining your kiln. However it is possible to avoid the dirty part. It seems that there are different grades of steel and some of these don't flake off during firing. Every steel bowl that I have purchased from thrift stores has
not flaked, yet every one that I've purchased new has. Go figure.
For the past few months I've used the faster-firing schedule Hadar Jacobson shared on her blog. It really does work with all brands of clay (or at least all the brands I've tried!). This firing schedule is two-phase, with the first phase completed on a gas stove. For this reason, I now only use stainless steel firing boxes and bowls. For awhile I used the lid from my fiberboard box as a lid on the steel bowl, but then I discovered that a aluminum foil pie plate with a few holes punched in it worked just as well (for the gas-stove step only - don't use aluminum in your kiln!). The photo above is my Pocket Rocket stove with a bowl full of metal clay creations hiding under that lid - and my supervisor Indigo in the background.
So there you have it - many options for firing your metal clay creations in carbon! My advice is to keep is simple and use a stainless steel bowl. More money for clay that way! Enjoy your weekend all! ~ Cindy Morris, gogoshebogo design
