Post subject: Heat treating Amethyst and Citrine at home
Posted: Thu May 17, 2007 10:34 pm
Gemology Online Übergod
Joined: Tue Aug 01, 2006 3:24 am Posts: 4997 Location: McDonough GA
When I was a kid I had several large citrines that I "tested" by heating them in the kitchen oven. As I recall they all lightened up in color. However, I also seem to remember that they eventually cracked when left in too long. But then, being a kid and not knowing any better, I had simply put them on a cookie sheet and cranked up the heat.
Now I'm looking at some fairly dark Ametrine I have and think a tat lighter shade would do the stone wonders. Is there a safe way to pack the stone so I can heat it up in the oven or do I even dare try?
Now I'm looking at some fairly dark Ametrine I have and think a tat lighter shade would do the stone wonders. Is there a safe way to pack the stone so I can heat it up in the oven or do I even dare try?
I recommend packing them in some Brownie batter. If the stones don't lighten, at least it won't be a total loss. If they do, you can market a new gem name, "Betty Crocker Ametrine."
Joined: Fri Feb 24, 2006 1:20 am Posts: 2756 Location: Southern California, U.S.A.
JB wrote:
Quote:
I recommend packing them in some Brownie batter. If the stones don't lighten, at least it won't be a total loss. If they do, you can market a new gem name, "Betty Crocker Ametrine."
And if you happen to have the Alice B. Toklas recipe you'll be happy with the results whatever they are.
I am not sure if this would apply, but enamel and glass bead makers use perlite to retain the heat after making them. By allowing them to cool slowly they are less likely to crackle.
Joined: Sun Nov 19, 2006 5:51 pm Posts: 481 Location: Las Cruces, NM
Jason,
The information I have here indicates that amethysts treat at temperatures of about 390 C to 450 C. If your oven gets that hot, I want one just like it. I couldn't find anything on citrine at first glance, so don't know about that part.
The perlite (or pumice, or clean sand can be used...) is used to insulate the stones while heating and cooling. Pack it around the stones in some sort of container so it hold the heat and creates more thermal mass. More mass means slower temperature changes, which is good. The other part of the equation is to bring the stones up to heat gradually, but especially cool them gradually. Some sources I've read call for 5*/hour, if I recall correctly. Sharp temperature drops will very likely cause them to shatter.
If you decide to give it a try, please keep us posted. I'm very curious about whether or not it would work.
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