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The Burner
The burners in Cambodia are not as secretive as in Thailande. This one accept to show us his workshop and the entire burning of our stones. The inner walls of those 2 shafts are made of red bricks vitrified and sealed one to the other by the heat.
The first step for th burner is to regroup
the stones depending on their reaction to the heat. They will be placed in different
aluminium oxyde capsules and they will be heated in different conditions of
temperatures and duration.
A first 2 hours heating process will confirm this distribution
made with naked eye. The real treatment will take the whole night for some stones,
a few hours for others.
THe burner brings two aluminium oxyde capsules that has been already used.
He removes the old ciment with a knife in order to be able to seal the crucibles properly. This mix of ciment, argile and other components is a secret formula which provide a special ciment able to resist to the high temperature and also able to remain airtight.
The stones are spread in the capsules. One the left you can
see smoe pink crystals which were probably some spodumen before the poor man
melted them by tried some heat treatment. We warned him but he didn't want to
listen.
Burners are barely real gemmologists but this is also the reason why they found
the berylium treatment by mixing some chrysoberyl with corundums. Thai burners
are reknown for their crazy experiments on expensive stones.
HE will now add what he calls the magic powder (probably borax) which prevent the stones to be sealed together and also avoid any thermal choc.
The crucible is hermetically sealed in order to create a reductive atmosphere which is used to enhence the blue color of sapphires by removing the yellow and brownish color created by Fe++. The purpose is to turn this iron into a Fe+++ configuration to allow the charge transfer with the Titanium (Fe+2, Ti+4)/(Fe+3, Ti+3) responsible for the blue coloration.
The burner will now put the small crucible in some bigger one made of that special ciment he previously used to seal them. The purpose is to slow down the diffusion of the heat and avoid any thermal choc. Some brocken pieces of ciment will be used in the same purpose to fill the empty spaces all around the small crucible.
