°C/min. At either 1 °C or 3 °C intervals, a pressurized pulse of compressed gas is imparted onto the surface of the sample. Multiple optical detectors continuously monitor the sample for movement. The lowest temperature at which movement is detected on the sample surface is determined to be the pour point. Measuring the pour point of crude oils Two pour points can be derived which can give an approximate temperature window depending on its thermal history. Within this temperature range, the sample may appear liquid or solid. This peculiarity happens because wax crystals form less readily when it has been heated within the past 24 hrs and contributes to the lower pour point. The upper pour point is measured by pouring the test sample directly into a test jar. The sample is then cooled and inspected for pour point as per the usual pour point method. The method usually gives higher pour point because the thermal history has not been cancelled by a prolonged thermal treatment. The lower pour point is measured by first pouring the sample into a stainless steel pressure vessel. The vessel is then screwed tight and heated to above 102 °C in an oil bath. After a specified time, the vessel is removed and cooled for a short while. The sample is then poured into a test jar and immediately closed with a cork carrying the thermometer. The sample is then cooled and then inspected for pour point as per the usual pour point method. See also Melting point Cloud point Cold filter plugging point Crude oil assay Gel point (petroleum) Petroleum Viscosity Wax References External links Some background knowledge about pour point and different measuring methods (manufacturer of pour point tester) USFS Pour Point and Product Fluidity of Various Class A Foams Phase Technology Manufacturer of ASTM D5949 automatic pour point analyzers Chemical properties Threshold temperatures