There are occasions, e.g. a mezuza in a sometimes-unbecoming environment, in which we're required to cover a holy object with one or two wrappings to separate it from various environmental elements. What are the necessary qualities of these wrappings?
Do they need to be opaque? If so how opaque? (At the extreme, would clear plastic work?)
Do they need to be watertight or airtight, or can they be porous? If the latter, how large can the holes be? (At the extreme, would a loose net bag work?)
Do they need to be durable? (At the extreme, would tissue paper work?)