For the last month or so I've been testing a new clay invented by Bill Struve of Metal Adventures and distributed by Cool Tools.
Introducing EZ960(tm) Sterling Silver Clay!
EZ960 is 96% Silver, 4% Copper. This is a lower copper content than traditional sterling, which is 7.5% copper. The advantage of the lower copper content is it does not require a carbon firing. It can be fired on an open shelf without any fire scale issues. The small addition of copper greatly increases the strength and hardness of the finished product, making it perfect for items that take a lot of abuse, such as hinges, rings and bracelets.
I made several projects while putting it through its paces, including a bracelet, hinged swing box, a ring, and of course, enameled pendants.
The wet clay has a lovely soft consistency and is not sticky. It has a tremendously long working time. It takes textures beautifully and is easy to sculpt and mold.
Once dry, it remains surprisingly flexible. I was able to make this bracelet by creating the separate links and then joining them together before firing. it was a piece of cake to open up the dry links to interlink the pieces.
Like most metal clays, the manufacturer is providing a number of firing schedules.
1675°F / 913°C - 2 hours
1700°F / 927°C - 1 hour
1725°F / 941°C - 15 minutes
I fired most of my pieces at 1675 for 2 hours. I got full sinter and had no trouble bending pieces. I did try firing at 1700 on one piece, but got blisters on the silver. My personal kilns do run hot, so this may not be a problem for others. I would recommend firing a few test strips to find the optimum schedule for your kiln.
My first piece stuck to the fiber shelf and discolored. I was able to clean off the discoloration, but it was difficult. On my second firing I used a piece of fiber paper as a barrier. This solved the sticking problem, but I still got discoloration on the down-facing side of the piece. Next I used vermiculite as a support. Third time's the charm! No sticking and no discoloration. You'll definitely want to fire the product on vermiculite.
The fired silver has a grayer color than .999 silver. This is normal for an alloy and should be expected. The fired EZ960 has a slightly grainy surface. It's not extreme, but it is noticable. Sterling, even at 4%, really is harder than fine silver, so cleaning up the graininess takes some effort. I did not get great results with my rotary tumbler. I had somewhat better results with my magnetic tumbler, but ultimately I got my best results with my flexshaft.
Smooth areas polish up like a dream. This stuff mirror finishes like nobody's business. The mirror finish I'm getting on EZ960 is superior to any other metal I've used, including .999 silver clays. Finishing textured surfaces was not quite as good. It's just not as easy to get rid of the slightly grainy effect on a texture.
With regards to patina, I was unable to achieve any colors with LOS. In fact, it took a very strong LOS solution to darken it. I had good results with BlackMax.
This brings us to what you really want to know. Can you enamel it?
The short answer is "yes", you can enamel it. If you put enamel on it and fire it, it will stick just fine. You don't even have to depletion gild it. I had no problem with it cracking or chipping.
BUT... 960 clay, whether you mix it yourself or buy it premixed, is NOT a substitute for .999 clay when it comes to enameling. There are problems with it that you need to be aware of.
The copper in the 960 causes oxidation issues. Transparent enamels come out cloudy and/or discolored. Even "good" results are not as crisp and clean as on .999.
In this photo you can see brownish specks in the enamel. This is copper oxidation. When enameling on copper you use a higher firing temperature to cause the oxidation to absorb into the enamel and disappear from the surface.
You might think the solution is to do a high firing here too. I knew what would happen, but I decided to go ahead and do it so you could see the results. A picture is worth a thousand words, right?
In this photo BOTH pieces have 2020 Clear for silver on them and nothing else.
When you high fire on silver it releases more silver salts into the enamel and causes massive discoloration.
The .999 sample was fired at my usual 1400 to 1450. The .960 sample was fired at 1550, my usual firing for COPPER, not silver. Yes, the oxidation spots are gone, but it's a mess. The yellow you see is silver contamination. The greenish tint is caused by the copper that was absorbed into the enamel. None of that is a problem on pure copper, but here its a disaster. If I were trying one of my more complicated shaded pieces I'd never get it to come out right.
At the end of the day, you have to ask yourself "Why am I trying to enamel .960 silver?" .999 silver clay is readily available and is PERFECT for enamels. Enamel pieces do not generally experience the wear and tear that make .960 desirable. If they did, your bigger concern would be chipping the enamel, not the strength of the underlaying silver.
The only justifiable reason I could come up with for enameling EZ960 would be for a ring. You probably can't see it in the photo, but there are fine bubbles and some clouding in this example.
If I were doing another ring with EZ960 I'd be inclined to stick to opaque enamels where such problems would not show up except for perhaps at the edges.
Unless you have a compelling reason for using .960, stick to .999 for enamels.
EZ960(tm) Sterling is a great addition to our metal clay family. If you are making bracelets, clasps, hinges, rings or other elements that take considerable wear it's a tremendous boon to have the added strength, and it's dead simple to use and fire.
Cool Tools is releasing the clay July 2016, but you can Pre-Order it now.