I heard somewhere years ago, that activated charcoal, like used in fish tank filters, was good to keep silver from tarnishing as well. It's a real drag when you buy some Mint condition coins, and they have the beginnings of tarnishing the next time you pull them out for a look. I put an empty plastic margarine tub full, with the lid off, inside my safe. So far so good.
The attractive natural toning usually comes from storage in canvas bags, and it usually only effects coins in direct contact with the canvas surface.
Storage in wood can cause tinting but it usually goes black on those contact surfaces.