Sunday, July 04, 2010

Gemstone tests

As I mentioned in a previous post new gemstones arrived at BeadFx. When I add a new material that I am unsure of I will test fire it out of clay to make sure it can withstand the time and temperature I intend to fire it at.

I took six of the new gemstones and tested them at 1650F for 2 hours to see if they would withstand to maximum temperature I would fire my silver metal clay creations. Here are the results, the stones on the LEFT are the test stones that have been fired :

Garnet Cz (no obvious colour change)

Lab created black saphire (no obvious colour change)

Aqua Cz (Oh oh, BIG CHANGE -FAILED all my tests)

Lab created Blue Spinels (no obvious colour change)

Lab created Ruby (no obvious colour change)

Lavender Cz (no obvious colour change)

It looks like all but the AQUA cz's survived. I retested the aqua cz's at 1200F for 30 minutes (the minimum I would fire at) and they failed yet again, they turned a lighter yellow brown. I torch fired one for two minutes and yet again I got a shade of brown. Disappointing as this stone would look awesome embedded into silver, of course you could set it in a fine silver setting after firing. I will test them in carbon in the next few weeks.

Lastly, I had mentioned my tests with a piece of Labradorite at 1650F here is a picture of what happened:

Remember, if your fire gemstones in metal clay DO NOT quench them, allow them to cool naturally or you may cause thermal shock and the stone may fracture.

1 comment:

The BeadFX Buyer said...

I'm not surprised by the colour change in the aqua CZ. Aqua CZ's cost about 3 times as much as the other colours because it's so difficult to get that colour. Even within a single batch there will be large differences in colour from almost clear to almost black/blue. Frustrating, because it is such a lovely colour.