- Five stemmed glass Sikes' hydrometers 34.29 cm long must be used in warehouse. Each stem covers 20 degree of indication. For shop inspection work, single stemmed glass hydrometers of proper range of brass gilt Sikes' hydrometers may be used. These instruments must never be used to prove spirit for duty purposes and hollow stemmed hydrometers open at the top must not be used or any account. Thermometers with wooden scale must not be used in warehouse.