oil content of petroleum wax - a measure of wax refinement, under conditions prescribed by test method ASTM D 721. The sample is dissolved in methyl ethyl ketone, and cooled to -32°C (-26°F) to precipitate the wax, which is then filtered out. The oil content of the remaining filtrate is determined by evaporating the solvent and weighing the residue. Generally, waxes with an oil content of 1.0 mass percent or less are known as refined waxes. Refined waxes are harder and have greater resistance to blocking (see blocking point) and staining than waxes with higher oil content. Waxes with an oil content up to 3.0 mass percent are generally referred to as scale waxes, and are used in applications where the slight color, odor, and taste imparted by the higher oil content can be tolerated. Semi-refined slack waxes may have oil contents up to 30 mass percent, and are used in non-critical applications. The distinction between scale and slack waxes at intermediate oil content levels (2-4 mass percent) is not clearly defined, and their suitability for particular applications depends upon properties other than oil content alone.