Thursday, 8 October 2015

Stone setting in silver clay

Sapphire and fine silver ring made by me!
Many jewellery makers haven’t heard of silver clay. It is a moldable material made from silver particles, an organic binder and a bit of water. Once the clay is dry it can be fired with a torch or in a kiln to burn away the binder to leave silver. It is a flexible way of working with silver and I’m often asked if stones can be pressed into the clay and fired. Sadly it’s not as simple as that! Some stones can be fired in place, others are damaged by the heat of the kiln/torch and these stones need to be set in a more traditional way familiar to silversmiths e.g. using a bezel setting.


However, there are some stones that can be set and fired in the clay and here is some advice about using these.


Cubic zirconia
Cubic zirconia are manmade stones that come in different shapes, sizes and colours. They are a very flexible stone for silver clay as they can be fired in place, both with a torch or in a kiln.


Hints
  • You do need to be wary of czs that lose their colour when heated and it is worth testing them by heating them safely with a butane torch for 30 seconds to a minute to ensure the colour stays
  • Ensure you push the stone so that the table (top) of the stone is level with the silver clay. This will ensure the silver clay shrinks around the stone to hold it in rather than popping it out
  • After you’ve fired the silver clay and cz do not quench the piece (put it in water), let the piece cool naturally (I have seen czs shatter when going from hot to cold through quenching).
  • At the jewellery school we buy our czs from metal clay as they are tested as kiln safe and come in a wide range of colours and shapes.



Dichroic glass
Although, of course, not technically a stone, dichroic glass can be fired in place in silver clay. Dichroic glass cabochons can be very brightly coloured and a lovely addition to silver.
You can embed the glass in the silver, it will shrink slightly around the glass and hold it in place. This can be torch fired (when the silver is dry) as the glass is not as affected by extremes of heat and cool but let the piece cool naturally, do not quench.


Hints
  • For both torch firing and kiln firing, place the pieces onto thinfire paper (particularly if the glass might be in contact with the firing block/kiln shelf)
  • You want to make sure the piece is level as the glass can begin to melt
  • Kiln fire on a full ramp at 700 degrees celcius for 15 minutes. Ensure the ceramic plug is our/vent is open to ensure the fumes can escape as these can affect the glass
  • Allow the kiln to cool naturally before opening the kiln door
  • For more information have a look at this article from the metal clay academy



Half drilled pearls/stones
You may have seen that you can buy half drilled pearls and stones. These, as the name suggests, are drilled part of the way into the bead rather than all the way through. You can add these to your silver clay designs by embedding a piece of fine silver wire into your piece.


Hints
  • You need to use 999 fine silver wire, sterling silver becomes brittle at high temperatures
  • Ensure the thickness of the wire fits the hole in the bead
  • Fire this piece as you would any silver clay piece, I suggest in a kiln if possible as silver wire is easy to melt when torch firing
  • Do any polishing you want to do before adding the bead
  • Once the piece is polished and ready to add the pearl/stone, cut the wire to the correct length to take the bead and add some epoxy glue to the end of the wire. Thread the bead on and hold it for 30 seconds to ensure it adheres
  • Allow the glue to dry completely before wearing (check the drying time of the glue you used)


Man made stones
The reason many natural stones cannot be fired in place in silver clay is that they have natural fissures/holes in them. The heat from the kiln or torch expands inside these fissures which can cause them to break and crack. However, there are some manmade stones that don’t have these fissures and can be fired in place. I have used lab created blue sapphires, red rubies and blue spinel. Unfortunately the stockist I used has recently closed so I cannot recommend a stockist personally. I recommend you try heating the stones first as I mentioned with the czs to check that they keep their colour before incorporating them into your designs.


Stones that can be fired in place
The US supplier cool tools has put together a very comprehensive guide of the natural stones that can be fired either with a torch or in a kiln. It’s an invaluable guide and you can find it here. Refer to this to see if your favourite stone can be fired.

I wrote this blog post for the London Jewellery School blog

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