ASTM D1465 Standard Test Method for Blocking and Picking Points of Petroleum Wax
11. Procedure
11.1 The blocking plate may be left on continuously. If starting with a cold plate, allow at least 3 h for the plate to heat up and reach an equilibrium condition with the pads and weights in place. Check the temperature recorder to be sure the plate is at the desired temperature.
11.2 The blocking plates have room for seven or eight rows of specimens across the plate. Fold the specimens to the length of the test section with the surfaces face to face. Cut single unwaxed glassine paper strips (or glassine, if desired) the same size as the folded, waxed test specimen. Insert the folded waxed specimen between the two unwaxed strips and place it longitudinally on the blocking plate with the folded end on the "start" line at the hot end. Place a second waxed specimen and an unwaxed strip in a similar manner on top of the first specimen. Not more than two of these test specimens should be placed in each testing space. Carefully smooth out the wrinkles in the specimens. Place any other specimens to be tested in other rows on the blocking bar in the same manner. If the blocking plate is not filled to capacity with specimens, insert sponge rubber pads and weights in the empty spaces.
11.3 After 17 h exposure on the blocking plate, remove the specimens together with the unwaxed spacer strips. Cool them for a minimum of 5 min. Carefully peel off the unwaxed strips and pull the specimens apart starting at cold end at a rate of about 152 mm (6 in.)/s.
11.4 Examine the test surfaces closely and mark the picking point and the 50 % blocking point. The picking point is the first of a series of spots of actual film disruption nearest the "cold" end of the strip. The 50 % blocking point is the first point nearest the cold end where 50 % of the width of the strip shows film disruption. Fine, isolated lines across the strip are not rated as the 50 % blocking point. Loss of gloss or spotting without film disruption is not considered as blocking or picking.
NOTE 2 - Several techniques have been used for viewing the test strips. These include viewing against reflected light, dusting the strips with graphite, or placing an opaque object behind the test strip.
NOTE 3 - Loss of gloss (blooming) can sometimes be distinguished from film disruption by lightly wiping the surface of the test paper with a cotton gauze pad.
