Here is how to heat Zircon.You place them flawless,must be real
clean or they will crack,and even then may crack,in a crucible
with activated charcol.This can be bought at any chemical
supply,usually the smallest containers are $30+/-.Activated
charcol is the best to use but there is another way.(excluding
gas).Activated charcol will work without any smoke.The other way
is to put sugar in the crucible,but it starts to put out a lot of
smoke when you get up to 600C or more.Stops around 800C.But I
mean a lot of smoke!
You then must seal the crucible.A good way is window screen,and
just wall plaster overtop the screen.Let it dry.Fill in any
cracks after drying.You then take it up slow,the slower you
go,less breakage,all the way to 1,000C.Hold it 2 hours or so.The
rise,depending on your furnace can take all day or longer.And it
can take 5-6 hours to cool to cold.Don’t open the door hot,all
will crack.
Now here is some tricks.You will observe dead in the bottom of a
sealed crucible are the best Blues.near the top may be white.You
rotate them and do it again and the white ones will go Blue.If
you overheat them,you can do them again,and they will come back
Blue.Even light blues done again,will go to dark Blues.
Now here is a trick to get Orange and Reds.You might get some on
the top of a sealed Crucible.When you first open a sealed
Crucible you will go crazy.The whole top will be covered with
Reds and Oranges!But after a few minutes in the air all will
revert to White/light Blue,except a stone or two.These are stable
Reds and Oranges.
Now to get a high percentage to all Reds and Oranges do the same
heat treatment without the sugar and in an open crucible.In both
the methods,you will get better results with a full crucible.
I have never done Cambodian,but I have run tonnage of Nigerian
and some from I think Tanzania and some I think were from
Australia and a few old Antique Blues.
Mark Liccini
LICCINI
http:www.LICCINI.com 107C.Columbus Dr.#1A
E-mail:Mark@LICCINI.com Jersey City,N.J.07302
Phone/Fax:201-333-6332