bluing
/ˈbluːɪŋ/(亦作blueing)
noun
mass noun
1
- chiefly historical blue powder used to preserve the whiteness of laundry〈主史〉蓝色漂白粉, 上蓝剂。
2
- a greyish-blue finish on metal produced by heating（金属）烤蓝, 发蓝。