Reducing 24ct into 18ct WG

Jewelry Discussion
1

Hi Guys;
I’m about to reduce 24ct gold bar into an 18ct White gold, using platinum, can I use my old scrap 950-900 plat to reduce it? or only pure 999 plat with 999 gold?
have you tried before?
thx

2

Welcome to the Orchid community!
Yes, technically you can add platinum to 24K gold to get 18K. It does not matter whether it is 950 or 900 platinum as long as the platinum does not contain gold. There is a 950 Pt with 5% gold alloy used in Europe.
Assuming your platinum does not contain gold, you just add 75% 24K gold and 25% of your platinum to get 18K.
You can melt gold first and then add thin strips of platinum and watch the strip dissolve in gold.
Mind you, the 18K “white gold” will have a super high melting temperature (like a solder for platinum, about 1400C or 2550F!).
Also, metallurgically you could be creating an 18KW gold with poor mechanical properties, so I would caution you about making this 18K gold!!
Shan

1 Like
3

thanks Shanaithal;
it does have 95% plt 2% pal, 2% cu, 1% Ag…
I was only warned that if it has High Ag content it will brittle on the mill, however I’m reducing the gold to Cast it into a fine Tennis bracelet , so I’m worried that it might not run smooth on the vacuum casting machine to the finest details, also after the cast I’m also concerned about the mechanical quality of the final product when they link them and set the diamonds.
Have you had the chance to cast such an item with such a metal before?

Warm Regards
TJ

4

Hi TJ,
No, I haven’t cast an 18K gold containing platinum.
I looked at the gold-platinum phase diagram and made the assessment about possible issues with mechanical properties.
Shan

5

Hi Shan

i’m getting info that the melting point for 18ct wg with plat is 1100c temp.
have you tried and tested before and gave you 1400c Temp. ?

6

Hi TJ,
Like I mentioned before, no 18K with platinum was actually melted and cast. The liquidus I quoted was an approximate temperature obtained from the binary gold-platinum phase diagram. I’m interested in understanding how 1100C was arrived at.

7

1100c failed to cast completely.
I will be doing a 2ed run today with an attempt at 1400c and higher flask temp. at 700c.