Have heard that a copper penny will substitute for Magic Cast.
Was told the ratio was about 3/4 of a penny to one ounce of gold.
Does anyone know if this is true and if there is a more accurate
I don't know what Magic Cast is, but I would suspect that it is zinc.
The 14K yellow that I usually make contains 6.66% zinc. As remelting
this metal causes some of the zinc to evaporate off, eventually, my
yellow gold will start to turn pink and will begin to oxidize too
easily. I have gone to the length of bringing the metal to a white
heat to burn off the rest of the zinc, and then to replace the zinc
in the proper amount, but you may find this a little drastic.
Pennies made in the last 20 or so years are copper plated zinc. Your
formula is probably pretty close. Remember not to add so much zinc
as to lower the intended karat.
Bruce D. Holmgrain
JA Certified Master Bench Jeweler / CAD/CAM Solutions