ASTM D1465 Standard Test Method for Blocking and Picking Points of Petroleum Wax
9. Standardization of Apparatus
9.1 Turn the blocking plate on with all sponge rubber strips and metal blocks in position. Allow sufficient time (3 h minimum) for the plate to reach an equilibrium temperature condition.
9.2 Calibrate a 30-gauge "test" thermocouple as follows: Heat a beaker of water to about 43.3 °C (110 °F) and measure its temperature with a temperature measuring device which is accurate to 0.3 °C (0.5 °F). Insert the "test" thermocouple in the water and measure the temperature with a manual potentiometer which is accurate to at least +/- 0.5 °C (+/- 1 °F). A portable precision type potentiometer or a type K potentiometer, both of which are accurate to at least 0.5 °F (0.3 °C) in this temperature range, is preferred.
9.3 Lay the calibrated "test" thermocouple across the width of the plate with its junction directly over one of the imbedded thermocouples. Be sure that one of the sponge rubber strips covers the junction completely. Replace the weights on the rubber strips. After 3 min to 4 min, note the temperature readings on the hand potentiometer and the corresponding point on the recorder. If the reading of the test thermocouple plus its calibration factor is more than 0.5 °C (1 °F) from that of the recorder reading, check the accuracy of the recorder separately. If the recorder is satisfactory, the trouble may result from the thermocouple being damaged or not in solid contact with the plate. Replace this thermocouple, taking care to tamp it into place so that its junction is held firmly against the plate metal. Check the new thermocouple and each of the other imbedded thermocouples in a like manner. Note the calibration factor of each.
9.4 For best operation, install the blocking plate in a constant temperature room. Check the plate calibration periodically, after installing new thermocouples, or if the plate temperatures vary more than 0.5 °C (1 °F) from the normal conditions.
10. Preparation of Waxed Paper Test Specimens
10.1 Heat the wax sample to at least 22 °C (40 °F) above its expected melting or congealing point according to Test Method D87 or Test Method D938, using an air or water bath so as not to overheat portions of the sample. After cleaning the waxing device, fill the wax bath with the sample to be tested. Hold the wax bath and the doctor rods or squeeze rolls at a temperature at least 22 °C (40 °F) above the expected melting or congealing point of the wax. For machines not having positive temperature control (heated electrically or by hot water) of the doctor rods or squeeze rolls, use infrared lamps or precontact the rolls with hot wax to heat them to about the wax bath temperature.
10.2 Use paper conditioned at least a week at 23 °C +/- 2.0 °C (73 °F +/- 3.5 °F) and 50 % +/- 5 % relative humidity. Load the wax coating device with the paper passing through the wax bath. Coat the paper with 6.5 g/m2 to 10 g/m2 (4 lb/3000 ft2 to 6 lb/3000 ft2) of wax on one side and 3.2 g/m2 to 10 g/m2 (2 lb/3000 ft2 to 6 lb/3000 ft2 ) of wax on the other.
10.3 Cool the wax coated paper to room temperature in ambient air.
NOTE 1 - As an alternative procedure, the wax coated paper may be cooled by passage through a water bath. There is evidence, however, the water quenching can cause variation in picking and blocking point values obtained on some waxes.
10.4 Measure the coating weight using Test Method D2423, with the exception of substituting the blocking point strips in Test Method D1465 for the 100 mm by 100 mm square of waxed paper in Test Method D2423. If the weights are other than 6.5 g/m2 to 10 g/m2 (4 lb/ream to 6 lb/ream) of wax on the test surface and 3.2 g/m2 to 10 g/m2 (2 lb/ream to 6 lb/ream) of wax on the back side, prepare another waxed paper specimen.
10.5 If the coating weights are satisfactory, cut two test specimens from the waxed test paper, each specimen 25 mm (1 in.) wide and twice the length of the test section of the blocking plate.
10.6 Condition the waxed specimens for at least 24 h at 23 °C +/- 2.0 °C (73 °F +/- 3.5 °F) and 50 % +/- 5 % relative humidity.
