Can You Combine Fine or Sterling Silver Metal Clays, Different Brands, or Fabricated Components?
Let's say you are working on a fabulous piece and you run out of a particular brand or type of Silver Metal Clay. You could wait patiently for a package to arrive, but no, you want to finish it NOW!!!! "What would happen if I use another silver clay or brand?", you think to yourself. Or let's suppose at the onset of a project you know you just won't have enough of one clay, but you have several half-opened packages. "What if I combine those?" Adding another Metal Clay body to the mix is a matter of having the right working conditions for success.
Firing Conditions: In Carbon or Open Shelf Firing (including on an open kiln shelf, in vermiculite, on fiber blanket, or in alumina hydrate)
Shrinkage Rate of the Metal Clay
Let's look into the ins and outs of what works and what doesn't, and why. Once you understand the "why" you will be able to use your emergency clay stash with more confidence.
Can I Mix Different Fine Silver Metal Clay Brands In One Piece?
Yes, If the firing temperature and shrinkage rates are within a short range you can. To mitigate the distortion of larger shrinkage rates you would mix the clays well before starting, obtaining a shrinkage rate somewhere in between. Most but not all Fine Silvers can be fired to 1650˚F on the high end. I'd say check the packages, but not all companies print the high temperature, which still baffles me.
Distortion may occur when two separate parts are built and assembled and they have very different shrinkage rates.
Interestingly enough, the advantage of purposely doing this is for effect. Let's say you want a doming effect, you might layer a high shrinkage clay topped by a low shrinkage layer, but planning ahead is in order.
Can I Mix Fine Silver Metal Clay 999 and Sterling Silver Metal Clay 950 or 960 in One Piece?
Mostly Yes, because the open shelf firing for both makes the firing conditions right, but you have to watch the firing temperature. Many of the 950/960 brands have firing schedule options and as long as you don't go above 1650˚F you won't risk melting the Fine Silver.
I decided to finally use Pods made over 10 years ago of PMC 3 Fine Silver. These pieces literally traveled the world on buses and planes without breaking as examples for my Elegant Meadow Pods class. The design required delicate open details, so I wanted those elements to be super strong, so my own special blend of PMC Sterling 925 and Art Clay Fine Silver in a 50/50 ratio were combined. Shrinkage rates were similar and when a patina was added, using two separate brands and clays worked well together.
Can I Mix Fine Silver Metal Clay 999 and Sterling Silver Metal Clay 925 in One Piece?
No, because of the firing conditions! Regular Sterling Clay 925 (not 950 and 960 store-bought or hand-mixed) need carbon to properly sinter. Fine Silver on the other hand is an open shelf (no carbon) firing. Each needs special conditions to sinter properly. So firing conditions are not interchangeable or proper sintering won't take place.
Here is why: Sterling has an alloy of copper in it, this makes it stronger, HOWEVER, copper needs an oxygen reduced atmosphere to sinter...the carbon you fire it in performs that job preventing oxidation, which causes interference with the particles bonding together.
Fine Silver, which is a pure metal with no alloy needs oxygen to sinter, so an open-air, no carbon atmosphere is a must. You can place it on a shelf or fire in vermiculite because that doesn't change the atmosphere in which it fires.
Exceptions to Every Rule - (Just to confuse you of course)
If, however, you mix Sterling 925 Metal Clay and Fine Silver Metal Clay in the proper proportions say 50/50 for a 960 enriched Sterling Silver Metal Clay blend the need for carbon is not necessary. Since there is more fine silver in the mix to enrich it you can avoid the carbon mess, but obtain more strength. The advantage is a stronger metal because of the copper alloy which exists in the Sterling.
As far as strength goes the strength increases as you add more copper to the mix. This increased tensile strength proceeds in the list as follows:
Fine Silver - no carbon
960 Sterling (96% Silver, 4% Copper) - no carbon
950 Sterling (95% Silver 5% Copper - no carbon
925 Sterling (92.5% Silver with the rest 7.5% Copper) carbon needed
This means you can't add the clays when wet individually in the same piece. If you choose one type of firing over the other, one of the clay bodies WILL NOT SINTER. But if mixed 50/50 well in the wet lump stage they will. Strange but true.
Can we add Fine Silver and Sterling Silver Wire or Sheet or Pre-fired Metal Clay parts to our pieces?
Yes, you can add both Fine Silver to Silver Metal Clay in a number of ways:
Here is the skinny on Embedding Fine Silver or Sterling in a piece. You will get little if any distortion if embedding something small such as an eyelet. If there is a large area connection you will most likely get some distortion and pull away from the Metal Clay since the wire doesn't shrink and the Metal Clay does.
Embed Fine Silver Wire directly in Fine Silver or Sterling Metal Clay by notching the connection that is buried in the Clay so the Metal Clay can make a mechanical connection. Fire as normal.
Embed Sterling Silver Wire directly in Fine Silver Metal Clay in the same manner, but you have to lower the firing temperature to 1290˚F 10 mins. or the sterling will get brittle. (I am not a fan of firing this low - as I've said many times, I'm a high fire gal by choice)
Embed Sterling Silver Wire directly in Sterling Silver Metal Clay in the same manner. Since you will be firing in carbon you can fire as normal.
When soldering to Metal Clay all conditions apply to metalsmith standards, but many like to burnish the surface area to be soldered because of the porosity of the Metal Clay.
You can avoid distortion with a 2-part firing, meaning if each Metal Clay part has been pre-fired shrinkage has already taken place so connecting them together after firing will help you to avoid distortion. This is also true for adding bezel wire to a base when setting a stone. I use this technique in both my Romancing the Stone: reverse bezel setting and Bezel Setting like a Pro classes. For full details on Successful Post-Fired Connections see my blog.
There are so many really great clays on the market. Each clay has its own unique properties. Some shrink more to obtain tiny detail. Some are more flexible and have a longer working time. Some are more rigid and great for building and constructing forms. Others have great carving qualities. In the comments, why don't you add your favorites and why you like them.
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