You are on: SILVER CLAY / Firing

This is the magical part. The firing. Where your little piece of clay becomes pure metal. This needs to be done correctly to ensure a strong end result. Underfiring would cause a weak piece, and overfiring can melt it.

As mentioned earlier the clay can be fired with a handheld gas torch, on a kitchen or camping gas hob, or with a kiln, depending on size, shape and which clay you have used.

Torch firing

DRYING

Drying
The finished piece needs to be dried out before firing to avoid any damage. Either leave it in a warm spot for a day or more, or, use a kitchen oven, dehydrator, hot plate, hair dryer or heat gun to speed it up. Please download the drying chart from the Downloads page for the minimum drying times.

Don't rely completely on the "mirror test" - you know, the one where you put a warm piece on a mirror, leave for 20 seconds, and if you see a "cloud" on the mirror when you remove the piece, it is still wet. Well, the one time I had a piece literally explode whilst firing, I had used that test. I had made a very thick chunky piece, and I think what had happened was that with the speeded up heating from a heatgun, the outside dried so fast and so solid it didn't let out the moisture which was still trapped inside. I hadn't left the piece to dry for long enough, but the mirror test fooled me to believe it was ready. So, it is not 100% reliable. Ah, and two things are important for this check to work - the metal clay piece must be warm, straight from the drying, and the mirror (or steel or glass sheet) must be cold.

Filing
When bone dry, you can carefully shape, file, and sand your piece so all edges are smooth and all little burrs or nicks are removed. These would be very uncomfortable against the skin after becoming metal hard. And they will be much harder to remove after fired. The clay is brittle at this stage, so be careful to not put too much pressure on it, and support the piece well. A supporting rubber block is extremely handy for this.

This is one of the most important stages in working with metal clay if you want to produce a professional looking piece. It always surprises me how little time people spend on their finishing. It is so easy to do, it doesn't take long, and it transform a rough chunk of clay to a sparkling "gem". Try it - and when you think you're done, put on stronger magnification, turn on a bright light, check your piece - and you'll probably sand a little more!

FIRING
You can fire your piece in three different ways; with a gas torch, on a gas hob, or in a kiln. All three are absolutely fine for silver clay, as long as they are used correctly.

Firing PMC on gas hob
GAS HOB - Most kitchen gas hobs should be ok to use with Art Clay silver clay. If you don't have gas in your kitchen you can buy a gas camping burner. Place a stainless steel firing mesh over the flame to put your piece on. Suitable for pieces not larger than a 50p coin - the whole piece should be within the orange glow on the mesh.

Benefits
Cheap and quick. Easy and safe, as you just switch your hob on for the required time, then turn it off - as safe as cooking. Almost impossible to overheat or melt the piece.

Negatives
With flames underneath, it can be hard to see colour of the piece (i.e. is it hot enough). Limit to size. Not suitable for pieces with glass, porcelain, Paper Type, or burnable cores.

Firing PMC with gas torch
TORCH - Most kitchen, or creme brulee, torches are perfect for metal clay, just make sure it has a nice large-ish, quite bushy, flame. These run on butane which you get from your local newsagent. Requires a little practice to control the flame. To begine with, fire in a dimmed room so you can see the glow. Put your piece on a ceramic fibre brick, which you in turn place on a fireproof surface (just in case you drop your hot piece). Suitable for pieces under 25g.

Benefits
Cheap and quick. Easy to use. Easy to judge the temperature of a piece with a little practice, meaning you can be sure it has been fully sintered.

Negatives
You're working with a open flame, which can be dangerous if you're not careful. It is possible to overheat or melt the piece.

Firing PMC in a kiln
KILN - Any kiln that can hold 650C - 800C reliably will be fine for firing clay. Kilns with cone sitters, kilns that are made for firing ceramic, enamelling, glass fusing, UltraLite kilns, digitally controlled kilns - as long as you can hold the temperature reliably for the needed firing time, and you don't get very hot or cold spots - you'll be fine. You don't need to use kiln wash for metal clay, and you can fire safely on a soft fibre shelf.

Benefits
Super easy. Very safe. No risk of under- or overfiring. Fire large batches in one go. Allows you to fire cork clay, glass, and porcelain.

Negatives
The most expensive, and slowest, firing option

Since I got my kiln it's the only thing I use (unless I am very impatient or need to fire a small piece very quickly) as in my opinion it feels safer. I know the piece has had the correct temperature and has been fired for the correct length of time.

Please download the firing chart from the Downloads page and refer to this to make sure you fire your piece the correct length of time and at the right temperature. There isn't a problem with firing a piece for LONGER than is stated in the chart - just don't fire it for a shorter time, or at a higher temperature then recommended.

Metal clay artists over the world are now recommending that you use the highest possible temperature, and fire it for a little longer than recommended by the manufacturers, for added strength. For instance, the 650 clay can be fired at 800C. At this temperature the manufacturer's minimum firing time is 5 minutes. I usually fire most of my pieces at this temperature for 30-45 minutes, and I only fire at a lower temperature if any material inclusions are restricting me from using the higher temperature.

You will notice there is an additional shrinkage at higher temperatures and longer firing times, which tells me that the end result must also be slightly stronger - as the material will be denser.

Obviously you need to adjust the temperature as needed if you have included other materials in the clay.

On the Downloads page you'll also find detailed instructions for firing with a torch or on a gas hob.

AFTER FIRING - After the firing is done, you can either leave your pieces to cool where they are. Or, if you're in a real rush and they are made with only silver, you can quench them (dip them in cool water) to crash cool them. Just be careful, they're still extremely hot, so don't drop them on your feet, or new floor.

Yes, the pieces do come out white - not looking like the silver you expected. What you see is the natural surface of rough, un-burnished silver. This will change when you use a brass or steel wire brush. You can do this dry, or in a little soapy water. Just keep brushing to "close" the surface, and you'll soon see that lovely silver shine.

Depending on what finish you are after - matte or satin, mirror shine, antiqued - there are different ways to achieve this. Read more on the Finishing page.