What Is The Name Of The Acid Used To Test Silver?

, until we get pictures or you get professional advice we are just going to be going around in circles.

My dad has worked on transmissions for years he has always said the best welder he knew was a guy that could weld aluminum. Call around to some welding shops and ask if anyone there is confident with aluminum, just because he's in a smelly dirty welding shop and not a clean upstanding jeweler doesn't mean he's not good with metals.

Regardless of all the possible solutions, I still say leave well enough alone. Would be nice to have a photo of what your talking about. If nice enough, I still think the best, safest, most economical, smartest thing to do is use it as a gift to some girl. If she is a coin lover, might make her mad that someone ruined possibly great coins though. If a jewlery lover, should like this as a real novelty.

I bought a silver/nitric acid test kit (pinkish/orangish acid with a scratch stone) off ebay. It was cheap and only the tiniest drop is dispensed at a time... and a tiny drop is all that is needed. Apply a drop to the solder and it will quickly turn grey and fizz. Wipe off when the reaction subsides. You can use Q-tips and a solution of baking soda then a good rinse between applications. Use several applications. This has worked successfully for removing all traces of silver/gray coloured solder I have yet encountered... and I must've done a dozen or so coins by now... all with the same small bottle.

Photography is not my thing, but here's a typical application result I would expect... VVV

https://goccf.com/t/135907

I have been lucky and not yet encountered any gold solder. The little gold mounting beads on the above mounted coin, and the entire mount, were all done with a silver coloured solder... such a miniscule amount of solder that it (the solder) looked gold even under magnification. I have removed several mounted gold coins from gold jewellery and all were soldered with, well... nitric acid took care of it in short order.

>>>edited>>> punctuation

This is pure speculation

how about using cold as means to remove the soldering?
Different metals expand/contract diffrently, and if the part where the soldering hasnt formed an actual alloy with the gold, the gold and solder should contract diffrently when exposed to extreme cold...thus loosening the solder from the gold.

Has anyone tried with liquid nitrogen or is my thinking totally off?

There are a LOT of things that can cause instant and permanent death if used improperly (including water). But used with proper care liquid nitrogen is quite safe.