18k Rose Gold...
Last year we encountered a problem with an 18k rose gold alloy. Before I go into the problem I give a little back ground: we make our rose golds from scratch using oxygen free copper, fine silver and always 1/2% pure zinc no matter what the % of copper used. The zinc as I understand makes the alloy workable and cohesive.
On to the "problem" we cast a 2 inch by 3 inch frame for a cameo and two days later we got the call "that casting was no good, it just started crumbling apart while working on it." I immediately took the sprue left over from the casting (we still had it untouched from the casting) and I bent it around a ring mandrel twice, not even a crack! I got the part back and I could crumble it into little pieces. So being a tech head I started researching the problem. I found out that they had to solder nine small wires to the piece for pearls... the part weighed around two and a half ounces in 18k, so while soldering they would solder one wire and allow it to cool off between soldering. Not on purpose but just the time it took to grab the next wire and heat it up again.
That is when the problem occurs... During my research I discovered a post on a news group by Peter Rowe that explained it very well. An inter-metallic compound forms in the alloy causing it to crack and break at the grain boundary.
The solution is from an other post is a faster read, but go read Peter's post first. The following steps should be taken in between each soldering operation when assembling in any 18k rose gold. This does not seem to affect 14k rose as much but might if it is a high copper alloy (RED Gold).
"Before any working is done, anneal by heating to a dark red (around 900F). Allow the red glow to just barely disappear and then quench. And here's the trick. If you quench in water, you run the risk of sometimes cracking the metal. (if you quench in pickle it will strip the copper from the surface and make your rose gold turn bright GREEN) So instead, quench it in alcohol. Be careful not to set the alcohol aflame with your annealing torch, and plunge the hot gold into the alcohol quickly, so it's immediately totally immersed. Done that way, the alcohol will not ignite."
quoted text comes from this URL http://newsgroups.derkeiler.com/Archive/Rec/rec.crafts.jewelry/2005-08/msg00080.html
So that's what I know about it, hope its a help to anyone who might find some cast rose gold on their bench that needs some solder work.
On to the "problem" we cast a 2 inch by 3 inch frame for a cameo and two days later we got the call "that casting was no good, it just started crumbling apart while working on it." I immediately took the sprue left over from the casting (we still had it untouched from the casting) and I bent it around a ring mandrel twice, not even a crack! I got the part back and I could crumble it into little pieces. So being a tech head I started researching the problem. I found out that they had to solder nine small wires to the piece for pearls... the part weighed around two and a half ounces in 18k, so while soldering they would solder one wire and allow it to cool off between soldering. Not on purpose but just the time it took to grab the next wire and heat it up again.
That is when the problem occurs... During my research I discovered a post on a news group by Peter Rowe that explained it very well. An inter-metallic compound forms in the alloy causing it to crack and break at the grain boundary.
The solution is from an other post is a faster read, but go read Peter's post first. The following steps should be taken in between each soldering operation when assembling in any 18k rose gold. This does not seem to affect 14k rose as much but might if it is a high copper alloy (RED Gold).
"Before any working is done, anneal by heating to a dark red (around 900F). Allow the red glow to just barely disappear and then quench. And here's the trick. If you quench in water, you run the risk of sometimes cracking the metal. (if you quench in pickle it will strip the copper from the surface and make your rose gold turn bright GREEN) So instead, quench it in alcohol. Be careful not to set the alcohol aflame with your annealing torch, and plunge the hot gold into the alcohol quickly, so it's immediately totally immersed. Done that way, the alcohol will not ignite."
quoted text comes from this URL http://newsgroups.derkeiler.com/Archive/Rec/rec.crafts.jewelry/2005-08/msg00080.html
So that's what I know about it, hope its a help to anyone who might find some cast rose gold on their bench that needs some solder work.
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