Oxidizing Sterling Silver: Safe Methods & Alternatives

Question
Hello,
I was wondering how I can artificially oxidise Sterling Silver? I have read about 'liver of sulphur', but that's nowhere available to buy. I have also read about copper sulfate/salt and water and have tried that one. It does blacken the silver, I am just unsure if it would damage stones/fresh water pearls/glass? What is the easiest to use and doesnt' damage stones?
Thank you,
Kind Regards,
Ines

Answer
Greetings,
Liver of Sulphur is otherwise Potassium Sulphide - you used to be able to buy it at the chemist.
most jewellery supply houses will carry something like this.
As far as damage goes, I've never seen anything like this happen.....well not in 25 years.
Good Luck, P