The Alchemy of Metal Clay


Metal clay consists of micron-size particles of metal plus binder and water.  The binder and water grant malleability to the metal, so that it can be easily shaped in a variety of ways. 

Metal clay is moist and supple when taken from its package. Texture can easily be impressed on the surface and the clay can then formed in a variety of ways.  Once the clay is shaped, its water content should be allowed to dry out either naturally through air-drying (18 to 24 hours) or by use of a heating device (eg, hot plate, hair dryer, etc.) for 15 to 30 minutes.  In the water-dried state (more commonly called green wear), the binder is still actively holding the metal particles together. At this point sanding, filing, carving, and other techniques may be performed cautiously with the knowledge that the binder connection may be easily broken (but also easily repaired).

Once the design of an object is complete, high heat is applied to the piece either with a torch or in a kiln.  The first effect of the heating process is burnout of the binder.  This is observed when ignition of the binder causes an engulfment of the piece in flames. These flames will dissipate in a few seconds, and the continued application of heat will initiate the far less observable process of sintering: in which high heat promotes the attraction and bonding of the metal’s atoms.  The result is a solid mass of metal that has been compacted without melting to the point of liquefaction. All manufacturers of metal clay will suggest firing schedules for the proper sintering of their products. 

If silver is the clay’s metal component, the surface of a piece will appear white when sintering and cooling is completed. This is due to uneven crystals on the surface that prevent the reflection light in any color. But the finishing process of burnishing and polishing will compress the crystals, making the silver color visible.