This study reports a steady state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex particles. The latex films were prepared from pyrene (P)-labeled PS particles at room temperature and annealed at elevated temperatures for 5-, 10-, 20-, and 30-min time intervals above the glass transition (T-g) temperature of polystyrene. During the annealing processes, the transparency of the film changed considerably. Scattered light (I-sc) and fluorescence intensity (I-0P) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of latex films were monitored using photon transmission intensity, I-tr. Scanning electron microscopy (SEM) was used to detect variation in the physical structure of annealed films. Onset temperature for film formation, T-0, void closure, T-v, and healing temperatures, T-h, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were modeled and related activation energies were determined. (C) 2003 Elsevier Inc. All rights reserved.