Tuesday, 22 December 2009

Heat-treating tiger's eye in my oven

OK, not only to I torture my beads by crackling them, I also put tiger's eye in the oven to colour it. I've been aware for a long time that red and blue tiger's eye beads are heat-treated, but it wasn't until a beader at Pärlplatsen, a Swedish beading forum, brought up the subject that I felt an urge to test this myself. She in turn had gotten the tip to put here brownish tiger eye in a regular oven at maximum temperature from a stone and bead shop in Stockholm.

She heated the stones for an hour in her first try, I didn't really have the patience to wait that long. But still I got some nice results in the two sessions I did. I put the stones into the oven when it was cold and also let them slowly cool down before removing them from it after I had turned it off. So that I wouldn't get unfortunate results similar to my crackled beads...

I think I could get even better results if I had had more time, but I'm still pretty pleased with how some of the stones turned out. At the photo above you can see three tiger's eye pieces. The one on the left is unheated (by me at least). The stone in the middle took on a dark caramel tone that I like and the stone on the right, which was in the oven longer, became more reddish brown.

I also had a pair of stones in red tiger's eye. On was not the prettiest of stones and the other was a broken 16 mm round bead. Both I was willing to sacrifice. It's not easy to see much of a difference in the photo below, but they did change a bit (bead in the middle is for reference and untreated by me). The stone was heated the longest and turned a brownish purple, but also the streaks became lighter and much more visible. The bead is just a darker version of the untreated one.

I just put my stones and beads in the oven on a pan or aluminium foil, but after researching online I found a bit more "advanced" methods that used clean fine silica sand to embed the tiger's eye, thus keeping them from heating up and cooling down too fast. I did not heat my beads for such a long time as in the instructions I found online, nor did I let it cool down for so long, but on the other hand it is adapted for larger slabs of rock. Those instructions I came across can be found here.

1 comment:

  1. FYI Blue Tigers Eye isn't coloured due to heat. Its fibrous structure is due to embedded fibers of crocidolite in quartz. Quartz breaks down the asbestos and what's left is a large quantity of Iron which gives Tigers Eye its colour.


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