What materials should I avoid washing in the dishwasher?

Do not wash items made of acrylic (crazing may occur), wood (can crack and warp), iron (will rust), tin (will stain), pewter, brass, or bronze (will tarnish). Also avoid bone-handled utensils (handles may separate), adhesive-joined pieces (adhesives may loosen), and plastic items not marked as dishwasher-safe.