Wednesday, February 17, 2010

Working with Precious Metal Clay

This is my process of working with metal clay. I don't go into the detailed step-by-step of how it's done because there are so many great books out there (listed below) that do it so much better than I ever could. The purpose of this post is to share with clients how their jewelry is made.

One of my favorite mediums to work with, Precious Metal Clay, is a clay-like substance that is made of small particles of pure metal (such as silver) mixed with an organic binder and water. Metal clay can be shaped or cut just like any soft clay, by hand or using molds. After the clay dries, it can be fired in a kiln where the binder burns away, leaving the pure metal.

When working with Precious Metal Clay, or PMC, I use a large number of tools to mold, cut or shape the clay into the piece I'm trying to create. I've worked with rubber stamps, steel lettering stamps, cookie cutters, PMC molds and impression templates. One of the great features of PMC is that you can use simple household objects as tools. Really, anything that will make an impression in the clay can be used, but avoid aluminum tools as they cause chemical comtamination.

My favorite technique is to make impressions from objects that have special meaning. You may have seen the Antique Flower Impression Necklace where I used an antique silver sugar bowl my grandmother gave me.

(TIP) When I find an object I want to take an impression of, I use Playdough to test if the object will leave the desired impression before attempting it with the clay. For example, I tried many times to take an impression from antique flatware only to discover the markings in the flatware were not deep enough to make an impression in the clay.

Once I am ready to work with the clay, I lay out all the tools I'm going to need on my work space. PMC can dry out on you fairly quickly. (Esp in the the winter when I'm blasting the heater to keep warm) So I want all my tools within reach.

(TIP) I always talk through a 'plan of action' before I begin.

"1. roll out the clay with this rolling pen (touch the pen),

2. cut the clay with this cutter (touch the cutter), etc..."

This mental check list helps me determine if all of my tools are ready. If I'm really feeling obsessive, I will even make a mockup of the pieces I'm about to create with Playdough first.

Once everything is in place, I open the clay and get to work cutting, shaping, molding, whatever the piece calls for.

As you work, the clay becomes dry and leathery. Keep a spray bottle of water close by to remoisten the clay. I keep my scraps in an airtight container with a tiny damp sponge at the bottom.

Once I'm finished, I prefer to allow my pieces to air dry overnight. Some people use hotplates to speed up the process.

Once dry, the clay pieces have the consistency of chalk. If they aren't handled gently, they could easily crack or crumble. At this stage, I use fine grit sandpaper to smooth out the edges and create a smooth surface. (TIP) Fingernail files also work great to gently sand thicker pieces.

Next, the pieces are placed into a kiln where they are fired at a temp of 1100 degrees for 20-30 minutes. The firing process can take several hours as the kiln takes time to warm up to that high temp, maintain that temp for half and hour, then cool back down.

Once the pieces have cooled completely, they still aren't finished. They come out of the firing process hard as metal but with a dull, white, ashy finish. This is because the firing process has caused the surface of the silver to become crystalline which must be smoothed down and polished. A quick 'bath' with soapy water and a stainless steel brush does the trick.

Afterwards, you are left with a pieces that shines like a mirror.

This mirror finish is fine for some pieces, like this simple ring. But to make those impression pieces stand out, I usually oxidize my designs in a solution called Liver of Sulfur (which smells like rotten eggs). This solution causes the silver to artificially tarnish. Simply polish off the tarnish from the areas you don't want it and you're left with the contrasting black on silver.

There you have it!

That's my process of working with metal clay. I know I didn't go into the detailed step-by-step of how it's done, but there are so many great books out there that do it so much better than I ever could. Some of my favorites include:

The Art of Metal Clay by Sherri Haab


Magical Metal Clay Jewelry by Sue Heaser

If you are interested in learning more about working with Precious Metal Clay, I suggest taking a class at your local jewelry supply or bead shop. PMC can be a pricey medium to work with, so make sure you love it before making an investment in the tools.


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