A photon transmission method was used to probe the evolution of optical clarity during film formation from hard latex particles. The latex films were prepared from poly (methyl methacrylate) (PMMA) particles, annealed at elevated temperatures in various time intervals above glass transition (T-g). Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed films. In order to mimic the latex film formation process, Monte Carlo simulations were performed for photon transmission through a rectangular lattice. The number of transmitted (N-tr) and scattered (N-sc) photons are calculated as a function of disappeared particle-particle interfaces. The increase in the transmitted photon intensity (I-tr) is attributed to the increase in "crossing density" at the junction surface. The backbone activation energy (Delta E) was measured and found to be around 33.4 kcal mol(-1) for a partially relaxing polymer chain across the junction surface. (C) 1998 Elsevier Science Ltd. All rights reserved.