How to solder so that the tin does not darken?

Question

Soldering

The other day I soldered (repaired) a miniature silver-colored metal product. It turned out that after soldering the tin turned black and now in some places it stands out strongly against the silver background. Pre-etched with soldering acid, since nothing was soldered at all. Soldered with pure tin. How to be? Should I take some other solder that will not darken? Or how to clean already soldered tin?

Answer 1

In general, this is still not a question about "soldering" in terms of electronics. Question about jewelry.
Tin will darken by definition. The only thing that can temporarily save the situation is mechanical processing. Polishing on coarse felt will remove both tin and traces of silver oxidation (if it is real silver). Although, judging by the description, this is not silver at all, because. silver would be soldered with tin without acid. Most likely, the product, at best, is silver plated. Here the silvering peeled off, revealing the blackness of the inner material. But polishing and in this situation will not be harmful.
And, in general, silver is soldered with special solder
www.livemaster.ru/item/3547581-materialy-dlya-tvor...
This is usually more than 50% silver with some additive that reduces the refractoriness - so that you can solder without the risk of melting the product. But, anyway, its melting temperature is not for a soldering iron.
Next time I recommend contacting a repairman-jeweler. It will cost 200-300 rubles.

Answer 2

I think there can be many factors, for example, solders with a high lead content darken, so if this decoration could darken from wearing (contact with the body), or if it is not silver, but just silver, then specify what kind of metal.