What items should NOT be washed in the dishwasher?

Items that should not be washed in the dishwasher include wooden items (which may warp, crack, or discolor), cast iron (which will rust and lose its seasoning), pewter and tin (which will discolor), and plastic items not marked 'dishwasher safe.' Antique or hand-painted china, delicate crystal, and gold-plated flatware should also be handled with caution, and you should always check the manufacturer's recommendations before washing.