Dynamics of liquid film rupture under local heating

•Measurement of ultra-thin liquid film thickness is possible using the adapted confocal method.•Thermocapillary rupture of a liquid film can be divided into three stages.•Residual film covers the heater before the dry spot forms.•The thickness of the residual film was found to strongly depend on the liquid viscosity.•The data obtained for various working liquids were generalized by a dimensionless correlation.