Photon reflection method was used to monitor the evolution of transparency during film formation from latex particles. Latex films were prepared from Poly (methyl methacrylate) (PMMA) particles, which were annealed at elevated temperatures in various time intervals during which reflected photon intensity, I-rf was measured. I-rf first decreased and then increased as the annealing temperature is increased. Decrease in I-rf was explained with the void closure mechanism. Increase in I-rf against temperature was attributed to increase in crossing density at the junction surface. The void closure constant, B and the back and forth activation energy (Delta E-rf) were measured and found to be around 24 x 10(3) K and 49 kcal/mol respectively.