At present, the soft processing of materials attracts considerable interest. Chemical bath deposition (CBD) effects film formation by means of a controlled chemical reaction. Adherent, uniform and reproducible films of zinc sulfide (ZnS) have been deposited, upon low iron-content microscope slides, under acidic conditions, from a solution containing zinc chloride, urea and thioacetamide. Scanning electron micrographs of the deposited layers suggest that, as the reaction proceeds, uniform film growth is associated with increasing particle size, rather than continuous nucleation and deposition of new primary particles. Energy Dispersive Analysis by X-Rays (EDAX) spectra are typical of CBD-deposited films of ZnS; signals attributable to elements within the glass substrate are also detected, an observation consistent with the thin nature of the films. Grain size distributions have been investigated using computational image analysis, and an average increase in the diameter of the deposited particles of 33.7 nanometres per hour has been calculated.