Before embedding anything that you are unsure of how it will handle the temperatures of firing metal clay it is best to test fire the item (so that you don't waste your clay). First, I researched the melting point of nickel = 1453 Celsius (not sure what that is in Fahrenheit). That temperature suggests it should work. Knowing that even though a melting point is high doesn't necessarily mean it will tolerate high temperature firing (for example Sterling can become brittle if fired at a temperature too high), I decided to test fire a nickel pin back (without clay).
Test Firing: Torch firing - Before I kiln fired the nickel piece I tested it with my torch as if it doesn't tolerate the heat of my torch the likelihood of it tolerating the kiln would be slim. The piece survived so on to test 2.
- Kiln Firing - I fired the backing in the kiln at 1550F for 1 hour. The result....the pin back survived but turned black so I tried a third test.
- Kiln Firing in Carbon - It seems the carbon to help reduce oxidization so I test fired a pin back in carbon. The result less blackening, it did loose its luster but it was satisfactory enough for me to proceed with embedding it in a silver piece.
Now that I knew that the nickel would survive kiln firing ...now I needed to test its ability to be embedded into silver clay. So I made my piece and to put the backing in.
I used the nickel backs pictured above (at the beginning of the post) from BeadFx - item # 24211265 - at 27 cents a piece they are inexpensive to experiment with....
I cut the pin backs (reason - I was concerned that as the clay shrank around the full pin back I would get cracking...didn't test this).Cut Pin Backs (I do not use the middle section, only to help place the pieces, then discard)
The first attempt at embedding the pins was a failure. I put the backs on a treble clef that did not have a smooth flat surface (this can be a little more challenging, leave it to me to experiment the hardest way). I used syringe paste to paste the pin back pieces onto the treble clef. The result after firing was some slight cracking in the clay and the nickel pin back was able to be pulled of with some force.Pin back pieces embedded in soft balls of clay.
The second attempt I embedded the pin pieces into a ball of soft clay then attached to balls to the dry treble clef piece. This time success!!! The pieces fired successfully but as noted the pins do discolour slightly and should be fired in carbon. (NOTE: To fire silver clay in carbon, first torch fire the dry piece to allow the binder to burn off, I do this by heating the piece allowing it to catch on fire, removing the flame, then allowing the flame to burn out then heating again until the piece no longer catches on fire)
RESULTS: The pin back attached but discoloured and when tumbled the pin backs rust slightly. Once tumbles I used my dremel tool to remove the discolouration and any rust. The use of the nickel pin backs work but may not be the finest finding for your precious metal clay pieces. Personally, when money is tight it may be an option for you. They should work great with the base metal clays which I will be trying next.
Overall, the nickel is not a good option for fine finishing and is not for everyone but can work in a pinch with a little extra effort. For best results I would recommend using the fine silver findings I talked about last week, but they are more expensive. I will let you know how theses nickel pin backs work with the variety of base metal clay I use later on....