Firing COPPRclay™ is a process that uses low heat to prepare the kiln's atmosphere and vaporize the binder and high heat to sinter the alloy. COPPRclay™ must be fired in a kiln. During firing, the
non-toxic binder vaporizes, leaving a solid, pure copper object.
Note: Make sure your piece is completely dry before firing; it's not a problem for the piece to dry for weeks before firing, but firing a piece while it's still damp can cause the moisture to expand, creating blisters.
To reduce oxidation, the clay piece(s) must be surrounded by coconut shell-based activated carbon (#703-205) during firing. The activated carbon tends to produce a natural terra cotta color. Important: COPPRclay™ can only be fired in the coconut shell-based carbon; do not fire it in the coal-based carbon (which can be used when firing BRONZclay™) as the piece
will not sinter properly and may break easily.
To Fire COPPRclay™:
1) Spread 1" of coconut shell–based activated carbon granules on the bottom of a stainless steel firing pan (#703-202, #703-206). Remember, COPPRclay™ can only be fired in the coconut shell-based carbon.
2) Place the piece on top of the layer; if firing two or more pieces, leave at least 1/2" between pieces; leave more if the pieces are larger.
Note: Most front-loading kilns are cooler in the front near the door, so the front of your firing pan will be cooler than the back and sides. To compensate for this, place pieces closer to the sides and back of the firing container. If you're using a top-loading kiln, there's no need to adjust. Avoid the front of the pan when using a front-loading kiln.
3) Pour more activated carbon granules on top of the piece until the container is filled 1" from the top, making sure there is a 1/2" layer of granules on top of the piece. If you are firing several pieces in layers, make sure there is at least 1/2" of space between the vertical layers as well. Note: Do not fire more than 100 grams of clay at once; overloading may cause poor sintering.
4) Cover the firing pan with its lid and place it in the kiln on 1" stilts to allow good heat circulation. Fire clay according the the firing schedule show below:
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.
COPPRclay™ Firing Schedule (for pieces that will be enamelled):
If you plan on enamelling your fired COPPRclay™ piece, follow the two-phase firing schedule below using only the coconut shell–based activated carbon.
Warning! The firing pan will be extremely hot; do not touch! Allow the pan to cool completely before removing the lid. We recommend wearing heat-resistant gloves such as Rio 12" welding gloves (#350-051 and #350-050) while removing the firing pan.
5) The firing pan should be allowed to cool completely before removing it from the kiln; however, if you need to use your kiln again right away, you can move the pan to a heat-resistant surface (e.g.: a soldering pad or ceramic tile) and allow it to cool there.
6) Once the firing pan and carbon have cooled (you can hold your hand just above the firing pan comfortably), remove the fired pieces from the carbon bed and place them on a heat-resistant surface to finish cooling. You can re-use the activated carbon until you notice it starting to break down (broken grains and a sooty appearance). Note: If there are no stones embedded in the piece, it can be quenched in water at this time.