I fired a silver clay pendant with a dichroic stone in at 680 degrees centigrade for 45 minutes. When I took it out it was a silvery-white colour and I am having terrible trouble getting a nice finish on it. I have a feeling it should have looked completely white when it came out of the kiln and don't know if I have under-fired or over-fired. If I have under-fired can anyone recommend how long and at what heat I should put it back in the kiln? I would be grateful for any help with this. Thanks.