Ashing is a test to deduce the amount of ash forming material present in a petroleum product so as to decide its use in certain applications. Ash-forming materials are considered to be undesirable impurities or contaminants. The specimen is placed in a suitable vessel, evaporating dish or crucible and ignited. It is allowed to burn until only ash and carbon remains. The carbonaceous residue is reduced to ash by heating in a Muffle furnace at about 775oC, cooled and weighed.