I am very soon going to be making some gold alloys. While I have entertained the idea of high karat gold I likely will end up going with 14K gold for cost reasons. The question is, how much copper should I add to my fine gold to make it 14K? Most alloys seem to add about 27-29 percent but this seems like a little too much? Does anyone know how much copper I should be adding to my 24K to get it to 14K?
That seems to make 14K rose gold, what about for 14K yellow gold?
Amount of metal to add = (beginning karat – final karat) x beginning weight
divide this by Final karat
If equal amounts of copper and silver are to be added for yellow gold , half of the above will be
Copper and half will be silver.
Best to buy master alloys from a reliable source. You can choose from casting alloys, fabricating alloys and a multitude of colors. The pros have done the math and metallurgy for you. If you mess up alloying on your own you will have to pay a pro to refine your metal back to 24 kt. and start over.
One of my favorite mottos is Hire professionals and listen to their advice.
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Do you know a good place to buy fabrication master alloys?
Another advantage to master alloys is that they are made for specific uses. Some are for fabricating such a wire and sheet and forging. Others are for casting and have a formula for reducing oxides. The ones for casting are not very good for rolling or wire.
Buying master alloys may mean that you need an account from most suppliers and perhaps a purchase of alloy greater that you can use right away.
Let us know where you are (just in general, not your actual address) and someone close by may share what we have in stock to make this easy for you.
I would get some to you as an example.
Franklin
I live in B.C. in Canada. Thanks 
I have been looking at United Precious metals does anyone have experience with thier master alloys? I have heard wonderful thinks about the sterling master S88 but what about the gold alloys?
According to Oppi Untracht, Jewelry Concepts and Technology, for a dark yellow gold alloy that totals 1.710 grams, use 1 gram fine gold, .284 fine silver, .426 copper. This meets the British and European standard that the result must be 1/2k higher than stamped. See page 38 of the book for all varieties of gold and silver alloys.
That is very helpful! Thanks a lot! 
What about one for 18K? And 10K?
Legor Group USA has many in those colors and karats for both casting and mechanical work.
Cliff
Sorry no, I use Umicore in Ontario. They have some nice alloys and its a little easier on the wallet with the currency exchange rate of late.
Umicore Precious Metals Canada Inc
Markham, ON
(905) 475-9566
Aurora
I live in B.C. in Canada. Thanks I have been
looking at United Precious metals does anyone have experience with
thier master alloys? I have heard wonderful thinks about the
sterling master S88 but what about the gold alloys?
Best advice!
All the formulas are readily available as far as fine/alloy ratios. I would follow Jo Haemer’s advice and buy specific alloys. Hoover&Strong, United and a couple of others.