The film formation of 300 nm poly (butyl - acryl ate - co- styrene) colloidal particles is followed by adding up to 10 wt% of different solvents to the aqueous solutions and measuring how the temperature at which a clear film forms is changed. This temperature, called the cloudy-clear minimum film formation temperature, is related to the glass transition temperature of the polymer, which changes due to plasticization by the solvent. When present at 10 wt%, isopropanol is found to increase the glass transition temperature by 7 degrees C, whilst methanol reduces the glass transition temperature by 4 degrees C.