period of time the amount of coagulum collected at the end of the test was dried and weighed the weight of the coagulum was divided by the total weight of the dispersion and expressed as a percentage to give the value of stability settling stability was measured by centrifuging a known quantity of dispersion for a period of time at the end of the test the latex on top of the centrifuge tube was discarded leaving the coagulum at the bottom the net weight of the coagulum was measured and was divided by the total weight of the dispersion and expressed as a percentage to give the value of stability critical film thickness was a measure of the maximum coating thickness on a test panel at which the surface was crack free rewetting was a measure of the wetting ability of the coating it was measured by dipping a test panel in a diluted dispersion and observing its ability to wet the surface the lower the solids level to wet the panel the better is its performance four samples of ptfe dispersions containing 19 3 wt of ptfe 754 ppm of apfo 3907 ppm of apfo based on the weight of ptfe and having a ph of 3 5 were processed as follows 1 the raw latex was stabilized with 18 wt of triton x 100 0 1 wt of nh 4 oh 30 wt aqueous solution was added to adjust the ph 2 it was then transferred into a lab thermal concentrator which was connected to a circulating temperature control bath with maximum temperature set.