http://www.paclp.com/product/ISL/lit_isl/FZP%205G2s.pdf
"The freezing point of jet fuel is defined as the temperature at which the last crystal melts when warming a fuel that has been previously cooled until hyrdocarbon crystals form"
http://www.expotechusa.com/catalogs%...g/05-Fuels.pdf
Page 94
The sample is cooled in the test chamber with constantly stirring. The sophisticated dynamic measurement system emits a light pulse every 0.58C from a coaxial fiber optic cable positioned above the test sample. The light pulse is then reflected off the silvered-bottom test jar to an optical sensor. The advanced software package analyzes the response of the light pulse. The initial appearance of crystallization is monitored by light scattering. The sample is then warmed up, and the temperature at which the hydrocarbon crystals disappear is recorded as the freezing point.