I make jewellery, and sometimes silver jewellery looks just too bright and new. I like to give it a patina to soften and age it. Normally this is done with Liver of Sulphur (potassium sulphide) which gives off nasty fumes. I'm not a big fan of nasty fumes, and always like to go for the simple solution, so I prefer to use an egg.
Start by hard boiling your egg. I put it in a pan of cold water, bring to the boil and boil for 7 minutes.
Don't bother peeling it, just cut roughly in half through the yolk while still warm. If it breaks up, it doesn't matter.
Put the egg and the silver into a sealed container (I use a jar with a lid, or else an old plastic food container) and leave somewhere warmish for 24 hours. Give it a shake after a few hours so that all parts of the jewellery are in contact with the eggy gasses.
Hold your nose, resist the temptation to eat the egg and throw it away. The jewellery will be black. Use some fine steel wool, a pan scourer, a rough cloth or the back of an old spoon (depending on the finish you want) to rub the patina off the raised areas of your jewellery, leaving the the recesses darker.
This is a piece made from silver clay paper which was cut, hole punched and layered. I fired it with a blow torch on the grate of our fireplace, and egg oxidised it. The oxidising works well on both matte and shiny finishes.