Calculating gold weight

[Nicola P]

Hi there. This is a maths query rather than a question for technical advice. A customer has asked me to make a ring from sentimental gold of which there is 13g of 22ct gold. I need to add a quantity of 9ct to make it 18ct. How do I calculate this quantity? This has never been my strong point - I shall stick to making jewellery!! I'd really appreciate an answer fairly quickly as it's the customers wedding band and there are deadlines to be met! Many thanks in anticipation!

[ps_bond]

5.7g
(to the nearest .1g)
Should give a fraction over 75% in the final mix, but you might want to go down to 5.6g to make sure it is definitely over 18k.

(do you want the working???)

The calculation is easier if you just add silver & copper to dilute it!

[Goldsmith]

Nicola,

Just remember one little point, if you are melting up old jewellery scrap, there may be solders on the pieces that will effect your final alloy, most who melt up old jewellery go through it and cut off any obvious solder joints before melting or else melt it all together and get the result assayed hoping for a good mix. If I was melting 22ct down to 18ct I would use fine silver as the additional alloy as Peter suggests.

James

James

[Nicola P]

Thanks both - much appreciated! No James, I have done all the checks previously and the 22ct are wedding bands and are stampings so no solder joins. the 9ct is much of the same so I don't need to do the usual and remove solder joins -thanks for the advice.
Best wishes
Nicola