Realcent.org

Does anyone here have access to, or has experience with using a XRF analyzer that determines the percentages of the metals in PM alloys?

I'm working on a project to melt scrap gold and cast a custom-made ring myself, and this is my first time at calculating a gold alloy.

I'm trading Ag for a 14K ring, an 18K ring, and a 1/4 oz gold coin from one of the RealCenters on here. I need to have those rings analyzed so I can calculate what needs to be added to end up with the 17K finished alloy that I want.

My rough calc shows that by adding a silver dime to the mix, it will be pretty close; but it could be on the edge of being green/yellow gold, instead of the yellow gold alloy I'm hoping for.

Can anyone help me out to get an analysis?

What is the exact composition of the alloy you are looking to produce?

I'm looking at this ternary plot:
http://en.wikipedia.org/wiki/Colored_gold
The sweet spot I'm shooting for is 70% Au, 15% Ag, and 15% Cu. That would turn out to be yellow gold, at slightly less than 17 Karats.

The two rings in question are yellow gold, but the percentages of Ag and Cu are unknown.
Yellow 18K gold has a range of 75% Au, 20% to 10% Ag, and 15% to 5% Cu
Yellow 14K gold has a range of 58.33% Au, 27% to 4% Ag, and 28% to 14% Cu

My first calculation was at 70% Au, 20% Ag, and 10% Cu. Plotted on the color chart that alloy is very close to the vertical line where yellow turns to green/yellow. Too close for comfort with the rings' alloys unknown.

Simply melting the three pieces of gold would result in 79.666% Au, with the Ag & Cu percents unknown. That would be a bit more than 19K gold, too soft for a ring. I can add small amounts of coin silver and copper wire to adjust my alloy to spec.

Of course, I made a cool little Excel calculator to make it easy to jigger the percentages.