Asphaltene adsorption from a toluene solution on a glass surface was studied as a function of concentration, at ambient temperature and atmospheric pressure. The thickness of the asphaltene film measured by ellipsometry was found to be in the 20-298 nm range. The film thickness was found to increase by 38-70 nm after 24 h. Solutions containing asphaltene mixtures from different crude oils result in significant variations in film thickness when compared with single asphaltene cases. For CN-Ceuta and DM153-Ceuta mixtures, a diminution was observed, whereas an increase was found with the DM153-Furrial mixture. Finally, the results attained with asphaltenes in which low molecular weight compounds have been removed suggest a film swelling effect due to the alkyl-type resins which are found to modify the colloidal properties of the aggregated asphaltenes in agreement with the literature.