Acid stain on a gold ring - how to remove?

[LoveforPGTipsMonkey]

Hi, have posted in housekeeping too but copying here as more traffic.

I've bought a ring in a second hand shop (good price) but when at home, have noticed a stain. It's on the outside and really annoying - I think the shop lighting was dim so I haven't noticed.
It looks like a testing acid stain as it's dark-ish copperish colour and has the petrol style rainbow effect. Worried that it's not a testing acid though but something corrosive - and that's why the price was good?

Have soaked in fairy liquid and then also tried rubbing with baking soda as advised, but not change! It's next to a small stone so need to use something that won't dull the stone too!

Grateful for advice!

Are you sure it isn't a gold plated ring with an area of plating having worn off? Or it could be solder if it has been mended by an amateur I'd take it to a manufacturing jeweller's for advice. They'll be able to give it a really good polish for you too.

thank you wow - was thinking I could DIY it, do you know how much a repolish would cost?
It's hallmarked so not plated, also not solder as it's at the front by a stone that set in gold (no claws) - not at the back where you'd change the size etc.

I think it was tested by a chemical for a higher carat, and as it's 9 carat, it stained.

I'd still take it to a jeweller - ask them if they can do anything to remove the mark and how much it would cost. Cleaning and polishing would be likely to be part of that. Their polishing equipment can give results which are better than you can achieve at home and are longer-lasting. The jeweller can probably tell you what the issue is too.

Solder isn't necessarily only going show at the back btw - any excess can flow either side of a repair or other join. Excess solder around a join should be cleaned off. When properly finished, you should see the join at all. That said, you can't normally heat the metal to solder it with stones in situ.

will do that, wow. You aer right that they are bound to do a better job. Interesting re solder - I'll look with a loupe for a join.

I work in a jewellers, the best thing to use is an eraser/rubber, followed by the buff side of the 4 in 1 nail files.

interesting kimmy, thanks! i'd have thought this was too soft, but next time will try. I went to the jeweller with this one, the assistant buffed with a special cloth and said that's all they can do as it's too deep in (I was very dubious). Thankfully the actual jeweller came out and took it off with the wheel instantly! for free thankfully.