Hi all, having a bit of an issue resizing a ring (it was cast from wax). The solder balls but doesn’t flow and the silver turn black, like it’s burnt… never seen something like this and I’m hoping the ring was indeed cast 925.
IMG_6875.pdf (13.1 MB)
Make sure the piece isn’t nickel-plated. Years ago, when I was working in a repair shop attached to a large retail store, we had an entire line of Chinese-made sterling rings that came in with a nickel plating. It was a real problem— the only way to size them was to sand off the plating in order to get them to take solder. Do not file the plating off, as nickel will dull your file very quickly. Moore’s discs work really well for this.
If it’s not plated, then the silver turning black—what you described as looking burnt and also visible in the photo—is most likely due to the copper content in the sterling oxidizing and forming copper oxide. That’s the black layer you’re seeing.
If the solder itself is turning black and refusing to flow, that usually means either the flux has been exhausted or the metal surface is too oxidized. Try using a more generous amount of flux and focus your heat on the ring itself, not the solder. That helps prevent the solder from balling up.
You probably know and have done this already, but just in case:
Thoroughly clean and pickle everything beforehand to remove any residual flux or oxides.
Freshly file the joint.
Use clean solder—ideally from a fresh batch or a different flow point if possible.
Flux both the joint and the solder.
A charcoal block can help by creating a mildly oxygen-reducing environment.
When soldering silver, a neutral flame—with a crisp blue cone and balanced oxygen-to-fuel ratio—is generally preferred. It minimizes oxidation and keeps the metal cleaner during the process.
If all else fails, it might be an issue with the metal itself, but for what it’s worth, I’ve worked with even 80% coin silver and never encountered the kind of persistent trouble you’re describing.
Anyway, I hope this helps. Let us know how it turns out.
Regards.
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You could be dealing with Rhodium plating on the ring. I take it it isn’t one you made?
I am afraid I can’t be much more help than that.
Don Meixner
I have to agree with the others- if it’s silver, it must have been plated… Nickle can be detected by dimethylglyoxime (DMG)… test kits on Amazon $44…Not worth it unless you are dealing with a lot of commercial stuff. Rhodium itself is in the platinum family of metals. It shouldn’t tarnish or blacken with heating… Therefore, I think that nickel is the most likely plating…The best way is already mentioned… pickle well and sand down the surfaces… use enough clean flux, heat the metal and not the solder… also I take it that it wasn’t a piece that you made from silver…as per DonMeixner
I have a few questions. Did you coat the ring with powdered boric acid mixed with denatured alcohol? What kind of flux are you using? What kind of torch? What kind of flame? Tight or soft?
Jo
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I have had to deal with rhodium plated silver jewelry. I HATE that stuff.
Silver that is rhodium plated usually has a nickel under plating. Yes you can directly plate rhodium on silver, but in doing so the expensive plating solution is contaminated.
When applying heat to nickel/rhodium on silver the plating blisters off and leaves a huge mess. It cannot be elctro stripped, but it must all be laboriously removed by hand. In the image attached to the original post I do not see any blistering. Just oxidation. This is why I have asked questions from the person posting about boric acid and denatured alcohol, what kind of flux, what kind of torch fuel, and what kind of flame.
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I think you are right… whatever it is, it’s still a mess! if the metal were cast, could be bad casting… or not enough good flux and an oxidizing flame… still needs to be picked well and cleaned up… sanding should also help… strip off any coatings and clean up the oxidation…
Thank you all for your replies! For some reason, the solder flowed after I used my bench mate’s torch… So maybe an issue with my flame
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