The contribution of viscous flow to void-closure processes during film formation with hard latex particles was studied. Film optical clarity was used to follow the progress of this event. The latex films were prepared from poly(methyl methacrylate) (PMMA) particles and annealed in 10 min time intervals above the glass transition (T-g) temperature. Scanning electron microscopy (SEM) was used to detect the variation in the physical structure of the annealed films. To mimic the latex film-formation process, Monte Carlo simulations were performed for photon transmission through the latex film and the number of transmitted and scattered photons are calculated as a function of the mean free path. A relation for transmitted light intensity, I-tr versus void closure (time)(1/2) (t(1/2)) was derived by using the Vogel-Fulcher viscosity equation. The viscosity constant, B, was produced using this I-tr(t(1/2)) relation at various temperatures and found to be 12.8 x 10(3) K. It is shown that Monte Carlo results justified the I-tr(t(1/2)) relation. (C) 1999 John Wiley & Sons, Inc.