Don’t be disheartened if a fired silver clay piece is brittle. You can strengthen it by firing again using a temperature and hold time shown below. You can also repair and re-fire broken pieces.
Silver clay is composed of silver particles held in a binder. For maximum strength, the silver must be fired hot enough and long enough to completely burn off the binder. Only then will all the silver particles fuse together.
For maximum strength, fire silver clay to these temperatures:
PMC (all versions): 1650 degrees F, hold for one hour
Art Clay Silver (all versions): 1600 degrees F, hold for one hour
If you include glass or other materials that cannot fire to 1600 – 1650 degrees F, then use a silver clay version that is designed to fire to a lower temperature. Or for maximum strength, fire the silver clay twice. The first time, fire the silver alone to a temperature above. The second time, fire the silver combined with the other material (such as glass) to a lower temperature.