As post-addition additive, silanes improve water resistance, wet scrub resistance and adhesion to substrate. By adding two silanes to a standard styrene-butyl-acrylate dispersion as post additive, we confirmed effectiveness in improving wet scrub resistance and fulfilling the EN 13300 - Class 1 requirement. However, looking into the performance after ageing at room temperature for 28 days, wet scrub resistance and paint viscosity dropped significantly after storage at 40 °C for 28 days. See Table 1 . ...