You can re-oxidise your jewellery at home using a simple nontoxic method that uses the natural sulphur found in eggs:

You will need an egg (or 2 if you are doing a few pieces of jewellery), your jewellery, and either a zip lock plastic bag or tub with an airtight lid (a clear one is best so you can see what’s happening)

First clean your jewellery warm soapy water (a soft toothbrush can be used) and dry thoroughly with a soft cloth.Boil your eggs, I find that it works best if they are over cooked you do not want a runny yolk!Whilst still warm put your eggs in your tub and smash them up including the shells, the smellier the eggs are the better as this is the sulphur that will turn the silver black.Put your jewellery in with the eggs whilst they are still warm and seal the tub/bag. You can leave it for a couple of hours or overnight, if your tub is clear you can watch the process.Remove your jewellery and again clean in warm soapy and dry soft cloth.Bin the eggs, do not eat them!