When your metal clay creations are ready to fire, how you fire will depend on what clay you are using. Bronze and copper clays have special firing requirements and use specialized tools. I address these tools and firing requirements in the Bronze and Copper clay areas of the Learning Center. For this article, we will focus on fine silver clay firing.
There are several ways to fire silver clay and the tools you will need depend upon the method chosen. Silver clay can be fired with a hand held butane torch, on a stove top, in a small enameling kiln, or in a table top jewelry kiln.
The best way to fire silver clay is in a digitally controlled table top jewelry kiln. This is because you can fire at the optimum time while maintaining the ideal temperature for the duration of the firing. Anything less than a digitally controlled table top jewelry kiln is a trade-off in the strength of the final product. This is not an opinion, but a fact. I'll explain the shortcomings of alternative firing methods below so you understand what the drawbacks are.
Table Top Jewelry Kiln
Either a digitally controlled kiln or one with an infinite control knob can be used. A digitally controlled kiln features an electronic controller that is programmed by the user for the specific clay to be fired, leaving you free to do other things while the firing is carried out from start to finish by the controller.
An infinite control knob is similar to a dial on an oven. It is turned to the desired temperature, but has to be watched during firing and adjusted constantly to keep it at the target temperature. This can be a drag on the user since you have to babysit the entire firing.
The tools used for either of these types of kilns, called "kiln furniture" are the same. For most silver clay firings, all that is needed is a kiln shelf and 4 kiln posts. Set the wares directly on the kiln shelf, set the kiln shelf on the posts and fire.
There are several choices for kiln shelves. The difference in price reflects the life-span of the kiln shelf. Inexpensive fiber shelves break down fairly quickly and must be replaced eventually. If you fire silver clay occasionally, you can easily get away with a ceramic fiber shelf. A hard ceramic shelf is about twice the price, but lasts a lifetime (or until it's dropped!). In general, a soldering board should not be used as a kiln shelf.
A kiln post is something that is used to elevate the kiln shelf so heat can circulate around it, which results in more even heating of the wares. Purchase in a set of 4. Use one post below each corner of the shelf. Kiln posts are available in 1/2 inch, 1 inch and 2 inch lengths. 1/2" kiln posts are all that are needed to elevate a single shelf. 1 inch posts can be used to separate shelves when more than one shelf is fired in a load. 2" kiln posts are usually used to separate kilns shelves when more than one shelf is fired in a load and additional space is needed for taller items being fired. A 2" kiln post can also be laid on it's side to make a 1" post out of it since they are 1" wide. While a kiln shelf can be set directly on the kiln floor, using posts makes it much easier to remove the shelf from the kiln.
Fiber Blanket (or Doll Prop)
When firing pieces that are hollow, round or need some support, they can be nestled on a fiber blanket to cradle them while firing and avoid a flat spot from sitting on a flat kiln shelf. A fiber blanket can only be used a couple of times before it breaks down and has to be discarded. You'll have no trouble recognizing when it's time to discard and replace your fiber blanket.
High Temperature Firing Dish with Alumina Hydrate or Vermiculite Media
A high temperature firing dish is traditionally used to melt metals, so they are designed to be heated to high temperatures over and over. For silver clay firings the dish is filled with alumina hydrate media (which is grainy or powdery) or vermiculite (which has larger particles) and pieces that need support are nestled in the media. The dish is set directly on the kiln floor, or can be set on a kiln post or a kiln shelf. Some recommend using flower pot bottoms for the dish, however terra cotta is a low-fired bisque that cracks and breaks within the first few firings and has to be discarded...not to mention that your kiln will need to be cleaned of the spilled contents.
Welding or Kevlar Gloves
When a firing is complete, the inside of the kiln will begin to cool, but it can take some time. For those who are in a hurry to get their treasures out of the kiln and finish them (who isn't!), gloves protect your hands from nasty burns. Gloves can be used to remove the kiln shelf from the kiln while it's hot. If you use leather gloves, get the super insulated welding type. A standard leather work glove will not give you the protection from heat that is needed. A welding glove is big and bulky, but will save your hands. Kevlar gloves are constructed from high temperature Kevlar material with a leather covering and will protect your hands even if the kiln shelf is red hot.
These are sometimes called Trinkit kilns. The two models available are the Amaco Enameling kiln and the Ultra Lite Beehive kiln. These tiny table top kilns are mainly used for enameling, keum boo and granulation techniques, but are also capable of firing silver clay. Firing is limited to small, flat pieces. Rings and beads can be fired, but they need to be turned and fired once on each side.
Amaco FA5E Enameling Kiln
The Amaco FA5E kiln has a 6" diameter heating element. The manufacturer claims the kiln will heat to and maintain 1600F, but the surface of the elements will be closer to 1700F and can easily melt silver clay. Silver clay should not be placed directly on the heating element. Place silver clay items on a firing screen to raise them above the elements. This kiln can handle as many pieces as you can fit on the firing screen. A small piece of fiber blanket can be used to support beads.
Ultra Lite Beehive Kiln
The Ultra Lite has a 3" diameter heating element. Silver clay pieces should not be placed directly on the heating element. For silver clay firing, the Ultra Lite requires special ceramic inserts placed on the heating element, and to control the temperature, the optional temperature control is needed. The kiln can run extra hot in areas where voltage is higher than 110V. The kiln is normally operated with the lid on to create the highest temperature, but in places where voltage is higher than 110V (in the US voltage ranges from 110 to 120V), it can run hotter than 1650F, which will melt silver clay. In this case, the lid is left off.
Used as a kiln shelf for the Amaco kiln. Place the screen on top of the kiln chamber, or fold the corners of firing screen down 90 degrees so it fits into the firing chamber of the kiln. The folded corners will act as the legs for the firing screen. Place the silver clay items on the screen, cover and turn the kiln on. Set your timer and add 15 minutes to compensate for the time needed to heat the kiln to temperature. After the firing is complete, unplug the kiln and allow the pieces to cool a few minutes before removing with fibergrip tweezers.
Stove Top Firing
Limited to small, flat pieces, no larger than a quarter. A firing screen is placed over a gas burner. The burner is turned on to locate the places where the screen glows. Note the spots, then turn off the heat. Silver clay items are placed on the "hot spots" with fibergrip tweezers and the heat is turned on again. Timing begins immediately. Fire for no less than 10 minutes. Do not attempt to bend or form stove fired silver clay.
Hand Held Butane or Other Torch
A small butane, propane or jewelers torch is used to heat and maintain a salmon colored glow to the silver clay piece. The torch is raised to reduce heat and lowered to increase heat and maintain the proper sintering temperature. Fibergrip tweezers are used to turn larger pieces and rings for proper sintering on both sides. A hand held torch can also be used with a high temperature firing dish and fiber blanket for firing beads and other items needing support. Since firing tends to be very short (2 to 5 minutes), the strength of the pieces are much less than those fired in a kiln for 2 hours. Do not attempt to bend or form torch fired silver clay.
Hand Held Butane Torch
Also called a micro torch or creme brulee torch. Must be able to reach and maintain a temperature of at least 1110F. Always use at least a triple refined butane gas. Anything less than a triple refined butane will quickly clog the flame nozzle and render the torch useless. Good quality butane can be found at plumbing supply, jewelers' supply and cigar stores. Some kitchen supply stores and home improvement stores carry a quality butane as well.
Soldering Board or Kiln Shelf
Choose a glass surface that has rounded corners and finished edges so you do not cut yourself on raw glass edges. Window glass is very thin and has sharp edges, so it is not a wise choice. A tempered glass cutting board is a good choice since the glass is harder to break, comes with nicely finished edges, and they often have feet that raise the board up off the table. Having a surface that is raised is a great way to keep your clay and work safe from tools.
Any type of kiln shelf or soldering board can be used for torch firing. Place the shelf on a heat-proof surface. Place the silver clay object on the shelf and heat to a salmon colored glow and hold for 2 minutes minimum.