Depending on the type of metal clay you are using, from original fine silver to base metal clays, there are a number of options for firing. This may include anything from a kiln to a simple hand-held torch.
One of the processes of creating jewelry with silver metal clay that got me addicted was the ability to use a something as simple as a butane torch for firing. In as little time as two minutes, I could have a beautiful pair of earrings or a pendant ready to wear.
TORCH FIRING — —
When teaching a beginner class, I only demonstrate torch firing as a way to help the students understand how easy it is to set up your metal clay studio with minimal cost.
There are a lot of U-tube videos on metal clay, but one of my favorite ones on torch firing is by Jeannette Froese LeBlanc https://youtu.be/OwwZ3RnkEHw.
Here are some additional tips to remember when torch firing your metal clay.
1. Always make sure you are in a well ventilated area and that your piece is not too large or complex. (These need to be fired in a kiln for a longer period of time.)
2. Allow your work to air dry overnight or place it on a coffee warmer or dehydrator until thoroughly dry. One of my favorite ways to test if the piece is dry is to place it onto a small mirror and wait 5-10 seconds, if there is condensation on the mirror when you remove the piece, it’s not quite dry yet.
3. Once the piece is thoroughly dry, place it on a soldering block or fire brick. My torch station consists of a ceramic tile under the brick/block, which is then set on either a fireproof surface or something that can be singed (like a piece of plywood).
If you are working on the kitchen counter and the piece rolls off the block you don’t want to scar the counter-top. I always have a fire extinguisher in easy reach.
4. Light the torch and hold it so the flame is nearly vertical with the tip of the cone, about 3/4″ away from the work. Within a minute, the piece will be enveloped in a soft flame as the binder burns away. Your first instinct is to pull the flame away from the piece. Don’t do that! The flame will soon go out by itself. Within another minute the piece will start to glow red. Continue heating until this becomes a bright and luminous color. At this point, glance at a clock.
5. Hold this color as uniformly as possible for at least 2-3 minutes (glancing away periodically to relieve your eyes). When the time is up, turn off the torch and allow the piece to cool at least until the red color is gone, at which point it can be quenched or left to air cool.
KILN FIRING — —
As I began to create more complex metal clay pieces and increased my production, I realized that my best option for firing was with a kiln. Utilizing a kiln allows me to fire larger pieces (in excess of 1”), as well as groups of smaller items, like earrings. This frees up my time up to get back to creating.
As with torch firing, I always ensure my pieces are completely dry. All types of metal clay can be fired in a kiln. As long as the kiln can ramp up to the required temperature (as high as 1650 degrees F (900 degrees C) for silver metal clay and can hold that temperature for anywhere from 10 minutes to 4 hours, it can be used for firing metal clay. Programmable kilns allow you to set the time and temperature for firing, which removes any guess work. It’s important to check the clay manufacturer’s time/temperature requirements to determine how high and how long clay must be fired.
The main issue with using a kiln, is that you want to make sure the temperature readings and hold times are accurate. If metal clay pieces are under-fired (fired at lower temperatures or for a shorter period of time than required), then they will not be fully sintered and will be subject to breakage. Alternatively, pieces fired too hot will melt. Kiln temperatures can drift slightly over the life of the kiln. So if you find that you are having firing issues, it is a good idea to test the actual temperatures in your kiln using a handheld pyrometer and compare that to the read out on the kiln’s display. This may result in the need to adjust the temperature (higher or lower temperature by as much as 25 degrees) or period of time (longer or shorter hold time).
I always place my work on a kiln shelf that has been elevated with kiln stilts. This allows the heat from the kiln to travel up, down, all around the pieces. I never place my pieces directly on the kiln floor.
Because metal clay may sometimes slump, flatten or warp as gravity acts on the metal during firing, it important to support the piece to help it retain its shape. If you are firing a complex piece (curved or shaped) that needs support, there are several ways to preserve the shape of your piece. The most common varieties of support are a fiber blanket or vermiculite. Vermiculite, which is a naturally occurring material, is my choice of support for my metal clay. It is easy to find – I buy mine at a local garden center and it works well. I just place it in a crucible and place my metal clay pieces on the vermiculite and fire. You can also place vermiculite directly on the kiln shelf. Fiber blanket can be used to support whole pieces. It can also be placed in negative spaces for support of hollow forms.
My final note on firing metal clay is on Safety:
You should always fire in a well-ventilated area or outside. If you’re torch firing, wear cotton; synthetic materials can melt and stick to the skin if burned. Tie back your hair, wear closed-toed shoes, and don’t wear loose-fitting clothes.
If you’re kiln-firing, follow the kiln manufacturer’s specifications on creating a safe firing station. My kiln is in my garage and placed on a concrete block kept well away from the wall of my garage. I always have a fire extinguisher close by when I’m firing either by torch or kiln.
About the author: Katherine lives in Southwest Louisiana and is a PMC Connection Instructor. She is a member of Louisiana Craft Guild and her class offerings range from introductory classes to Certification. Katherine teaches in her home studio, as well as at the New Orleans School of Art and Craft in New Orleans, Louisiana.
Katherine is one of four founding members of the L’ esprit du Metal, Louisiana Chapter of the PMC Guild where she serves as Treasurer and Secretary. Her jewelry can be found in several galleries both in Lafayette & New Orleans, LA including Sans Souci Gallery, Lafayette Art Association Gallery, Hermann-Grima-Gallier Historic Houses Gallery in New Orleans, LA.