Clean glassware is only demanded in good laboratory technique, because the most carefully executed piece of work may give an erroneous result if dirty glassware is used. In all instances, glassware must be physically clean; it must be chemically clean; and in many cases, it must be bacteriologically clean or sterile. Soap, detergent, or cleaning powder (with or without an abrasive) may be used mixing it with hot water while washing glasswares. For glassware that is exceptionally dirty, a cleaning powder with a mild abrasive action will give more satisfactory results. All glassware that is used in precise measuring of liquids should have fully wettable surfaces.
Some general washing rules are :