All glassware must be scrupulously clean. If it has been standing for any length of time, it must be rinsed before use. One test for cleanliness of glassware is that when filled with distilled water and then the water removed, the glass should contain only a unbroken film of water. If the water collects in drops, the vessel is dirty and must be cleaned. Many commercially available detergents are suitable for this purpose.
Some manufacturers have special formulations for the purpose of cleaning laboratory glassware.
Typically glassware is thoroughly cleaned with the detergent and rinsed three times with tap water. The outsides of a vessel may be dried with a lint-free cloth, which is reserved exclusively for this purpose and which is frequently laundered, but the cloth should not be used on the insides of the vessels.