About Metal Clay

What is metal clay, precious metal clay, art metal clay, art clay silver, silver clay, gold clay, bronze clay, copper clay, steel clay, etc.....?

A little History

Legend says it all started in the early 1990s when two Japanese companies each looked for new uses for those old heirlooms from the golden age of the "Silver Screen": film negatives. Too precious to throw away, the thousands and thousands of kilometres and miles and furlongs of film, all containing tiny bits of silver add up to a lot of potential $$$. Silver metal clay was invented and then gold clay quickly followed, and other metal clays eventually followed.

*** Note that originally the silver was repurposed from existing, archived, stores of film, which meant that the silver metal clay was more environmentally responsible than making objects using traditional methods using newly mined silver. So, yay! ***

Silver and Gold

The silver and gold in these clays is pure -- also known as "fine" -- and for years these remained the only two metal clays available. Except that fine precious metals are softer than and don't have the strength that their alloyed counterparts have and this posed a problem for items that needed to be more durable, i.e. rings.

So why didn't they just make alloyed versions? First, an alloy is a base metal that contains other base metal(s) in order to change their properties. Alloys of these precious metals generally use copper as the added ingredient, i.e. sterling silver is ~7.5% copper. Now, the problem with copper is that it quickly oxidizes in the presence of heat and oxygen. Oxidization causes metal surfaces to discolour and/or corrode as tarnish, rust, a patina, verdigris, etc. and this oxide interferes with the sintering process. (see Step 3 below)

So, in the years that followed, a race to find a method to overcome this oxidation obstacle was on and there were plenty of competitors. Ultimately, successful and mostly reliable methods and metal clay formulations were developed. This resulted in numerous new manufacturers offering their formulations and even other metals.

*** Nowadays, there are even recipes out there to blend your own clay at home, provided you like getting into the nitty gritty, and can source metals of sufficiently small sizes, and can find organic binders that are stable and don't make a mess when wet, and that completely and cleanly burn away. . . Fun, but one needs to weigh the costs, time, learning curve, and risks involved with getting it all figured out to decide whether it is worth it. And what would you rather do? Make clay or make art? ***

New Arrivals

This is when bronze metal clay, and soon thereafter a copper metal clay were introduced.

Oh the joy! Bronze and copper are not members of the "precious" club, making them so much more affordable than their silver and gold counterparts. Oh the freedom! And wow, did us consumers ever take full advantage!

But what happened to making the silver metal clay stronger and more durable? Where was the sterling silver metal clay? That took a little longer to fine tune, but, as you can guess, versions of these also, eventually, became available.

And that's not all! Different formulations of the clay produced different results, i.e. different bronze clays produced a variety of colours like "white bronze" and "golden bronze". And other alloys of other metals also came on the market, i.e. steel clay.

*** Bronze is an alloy of 89% copper and 11% tin, and generally, so too is bronze metal clay -- just like that used by our ancient ancestors. ***

What so is Metal Clay?

Metal "clay" is almost what the name says, only the "clay" contains metals instead of "clay minerals", and the result of firing the "clay" isn't a pottery or ceramic object, it is a metal object. A real metal object, not an object that looks like metal.

Metal clay consists of three primary components: the metal, a binder, and some water. The metal is in a powdered form as very tiny (in the microns size range) particles of a metal, i.e. gold, silver, copper. The binder is an organic binder which was once-upon-a-time a very secret substance that was often likened to corn starch, but wasn't, and is now generally known to be a pulverized cellulose. The water, is, well, water; but pure water (distilled) without any minerals. When the powdered metal, organic binder, and pure water are combined in the correct proportions, you have a highly malleable substance that looks, feels, and works like clay.

The Process

The process of transforming the "clay" into a "solid" metal object, consists of three main and unavoidable steps: (summarized and greatly simplified here)

Step 1 - Shape it into something. This is similar to working with pottery or modelling clay. You can roll the clay flat or into snakes or balls; press it into moulds or against textures; sculpt it; carve it; stick pieces together; refine the surface by texturing or water polishing it. Then repeat and refine until you are satisfied with the object you have created.

Step 2: Remove the water by drying it. The clay MUST be completely dry all the way through before proceeding to Step 3, or else, when any remaining water expands into steam and tries to escape, the object's surface can crack or blister, or it can even explode.

How to get it dry? Air dry, use a dehydrator, or heat it gently (slow and steady) at lower temperatures (i.e. less than Fahrenheit 451) usually using an oven, heating pad, or kiln.

Once dry, you will most likely return to Step 1 if you want to change anything, such as add to it, or repair any cracks or breaks (removing the water causes it to shrink), or carve into it, or refine the surface by smoothing or sanding or burnishing it, etc. Then you'll repeat Step 1 and Step 2 until you are completely satisfied with the object you have created and it is throughly dry all the way through.

It is important that you are satisfied before going on to Step 3 because it is generally far easier to make any changes while it is still "clay" instead of when it is "solid" metal.

Now you can proceed to Step 3.

Step 3: Fire the clay. In the case of metal clay this means the removing the binder and sintering the metal. The binder is a powdered, organic substance and the key here is that is organic (as opposed to inorganic) so that it will "completely" and "cleanly" burn away. Removal by burning requires heat. Lots of heat. Greater than your kitchen over can achieve. Temperatures significantly higher than 451 degrees Fahrenheit are needed. To a very limited extent, a common gas torch can be use. Ideally, a temperature controlled kiln is used to fire the clay. The object shrinks a bit more as the binder burns.

Once the organic binder is gone, it's the metal itself that shines -- literally -- as the microscopic particles get friendly with one another, and then the object shrinks even more as the particles fuse into a "solid" piece in a process called sintering.

Sintering: where ever each metal particle touches another, neighbouring metal particle, the particles' surfaces "melt" enough to stick (fuse) them together, but ONLY where they touch. So, between the particles, wherever they do not touch, tiny spaces remain*.

The Result

Then, there you have it! An object you've created yourself, that has been transformed from malleable clay into a new solid*, pure metal** object. And there it is in your hands -- once it has cooled to room temperature, of course -- and you're in awe, turning it over and around, feeling its weight, running your fingers over its textures, examining the colours and feel and heft of it . . . Or, at least that's what happens when I take my work out of my kiln. Your results and reactions may vary.

*** Want to see something cool? (Or hot, just not THAT kind of hot!) At least once, watch Step 3 in action. Use a gas torch on a small fine silver clay object. Watch as it browns, then burns bright, and shrinks, and settles down into shape, then glows and sort of shivers/flashes until it is a metallic pure white. By small object, I mean no larger than about the size of three stacked Canadian or US quarters (or 25 grams) because a hand-held torch doesn't have enough oomph for anything bigger -- unless you're willing to stand there for a very long time. OR, you can visit the links included at the bottom of the page for a video of this in action! ***

A Little Clarity

*Though "solid", it is not as solid (dense) as forged or cast metal because of all of those microscopic spaces that remain after the removal of the water and binder, and then the sintering processes. These spaces are called porosity. The advantage to this porosity is that the object will be lighter than one of equal size made in, for example, sterling silver, so your metal clay earrings won't stretch your earlobes as much as their hammered cousins would.

** Provided that all the binder burns cleanly away so no actual binder is left behind, and no other types of minerals or metals remain behind from the burnt binder, or from the water used to mix the clay, or other additives and detritus and substances used to work with the clay such as oils used to slow the drying process, or bits of leaves used for texture, or various organic substances used to support hollow-core structures. . . you get the idea.

What more can I say?

You are welcome to peruse my gallery for more images of pieces made from these metal clays, and, of course, you are welcome to contact me for more information. I am a PMC Level III Certified Instructor and an Art Clay Senior Instructor. Or, check these out:

General resources, manufacturers, organizations, instructors, etc. (alphabetically):

Art Clay World - www.artclayworld.com

Art in Metal Clay - artinsilver.com

Camp PMC - www.camppmc.com

IGS (International Gem Society) - www.gemsociety.org/article/precious-metal-clay-jewelry/

Metal Clay Academy - www.metalclayacademy.com

Metal Clay Alchemist - www.metalclayalchemist.ca

To see the drama of torch firing silver metal clay:

Torch Firing Metal Clay with Tim McCreight

Secrets of Torch Firing Fine Silver Metal Clay with Holly Gage

Getting Started in Metal Clay Torch Firing