Product Review: OneFire Sterling PMC

A beautiful bracelet by Terry Kovalcik made with Sterling PMC Photo: Corrin Jacobsen Kovalcik

I was recently asked by PMC Connection to test the new sterling metal clay by Mitsubishi.  I was excited, but also a little intimidated when I thought about all of the beautiful pieces made by testers of PMC products over the years: Hattie Sanderson’s rings, Celie Fago’s rings and charms, Terry Kovalcik’s bracelets. I worked hard on my experimental test pieces, but I didn’t end up with anything that will grace the posters and ads for the new clay. I did learn some things that I’m sharing in the hopes that my mistakes benefit other metal clay artists.

pmc-onefire-sterling-45g-50-6g-clay-weight-2962-pThe new “OneFire Sterling PMC” is a marvelous new clay.  Celie Fago’s idea to combine metal clays into a sterling 960 was a brilliant twist for metal clay artists.  And now Mitsubishi has taken the clay one step further and it can be open shelf fired.

Here is my review of the new clay:

WET FORM: It is a clay with a lot of plasticity. However, it rolls out nicely and holds its shape.  This clay also picks up textures easily. (A release agent was needed on “tear away” textures.  I used Cool Tools “Cool Slip”.)

DRY FORM: I found the clay to be very elastic while in the “green” stage or “bone dry”, which was a great thing for me when making rings.  You know that point you reach when making a ring and you are filling it and sanding it and the ring is essentially “done”?  But you go a bit further and then the ring breaks?  I didn’t have this happen. Yay!  But I wanted to know how a repair would work out, so I actually broke one of my rings.  I rejoined the two halves by painting only water on each side and held the two pieces together until I saw the water wick into the clay.  It was a great join and when fired I had a hard time finding where I broke the band.

A second ring I made intentionally thick so that I could carve it.  This clay carves beautifully.  Nice clean edges. This may be my favourite decorating/shaping technique with the new clay.

Firing: My mistake with the rings I fired was putting too much kiln fiber blanket inside the rings.  I wanted to help the rings hold their shape and not use an investment ring plug as I wanted to see what the real shrinkage would be. So I had the brilliant idea to use some kiln fiber blanket.  Some people use vermiculite to fire odd shaped metal clay pieces and I’ve always used fiber blanket without any issues. However, this time, I added too much kiln fiber blanket and two of the rings had their bands burst open.  I forgot that the shrinkage of this new clay was three rings sizes (15-20%) and I should have put in less fiber blanket.

Arrows point to where I filled in an opening between the band and the platform for the stone using hard-not dried out- clay. This is a sample of over filling. After firing this should be filed and sanded. The repair is strong.

Instead of worrying about the breaks, I saw it as a chance to see how repairs post firing would work out. This clay is easy to repair.  One ring band (in the photo) was totally open and the other ring’s band had stretched so far it tore open. I took some almost hard clay and forced it into the cracks with my fingers and metal tool. The repairs are strong, the clay sintered in those places.  (I tested the joints/repairs after firing by sawing across the joins. From the inside, there is no visual difference in the clay.  You can tell on the outside of the ring where the repair is but the repair clay adhered to the pre-fired ring shank.)


Before firing: this ring has many cz’s added…some right side up and some sideways and backwards. All stayed in place during firings!


Stones: A few artists I talked to about the new clay were skeptical that stones (CZ’s) would stay in the clay as the shrinkage could make them pop out. I tested that theory and to my delight, the stones stayed in!  I put the CZ’s in the clay so that the clay just cleared the edge of the girdle…and to push the limits I put some in upside down and backwards.  In firing, I covered the ring with fiber blanket and I let the kiln cool to 300 degrees Fahrenheit before opening the kiln door. Sucess!

Holes drilled for sterling wire to be soldered in place to hold the stone.
Mock up of the ring after adding the sterling silver prongs.

Wire: Another metal clay artist asked me to test with sterling silver wire. She wanted to know how to do it and would sterling wire fire with this new clay?  I made a ring with prongs made from sterling silver wire to test her questions.  I had figured that it would not work, but gave it a try just for the experiment. After firing the wire broke off very easily.  Two suggestions I have for those wanting to make a ring with prongs or wishing to insert wire.  Try using fine silver wire as opposed to sterling silver wire.  I haven’t tested this yet, but it is next on my list. Another option is to leave holes where you want the wire and to solder the sterling wire in place after the piece is fired. (See photos.)

Finishing: Out of the kiln this clay is easy to hammer and shape. It polishes quickly when tumbled and a mirror shine can be attained with sandpaper.

All in all a beautiful clay!  For a limited time, this clay has a promotional sale price! Thanks PMC Connection for the opportunity to test this fantastic new addition to the PMC family

540704_577388125607677_846842341_nJeannette Froese LeBlanc is the editor of Creative Fire and is an avid jewellery designer. You can find her jewellery online:

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