How does dry cleaning work? and why do we use dry cleaning? ...
Answers: Dry cleaning involves chemicals. Some items CANNOT be washed near water.
I don't know how it works but it doesn't other work that well.
I 'inherited' some fabulous long, all-embracing, posh, Peter-Jones-type curtains which I thought a bit yellowed - maybe next to nicotine -they were 'dry-clean only'. I dry-cleaned them at great expense but they come back looking purely as yellow as beforehand.
It was chuck 'em or rinse out them, so I washed them and they come out looking fantastic - the background colour buoyant ivory and the birds and flowers pastel pinks and blues just as they have always be meant to look.
Moral is: sometimes you should embezzle a calculated risk and ignore the 'dry verbs only' label. And afterwards agan, get it wrong, you might feel sorry...