Combination method of digital holography and gravimetric measurement for assessment of a paint drying process

A combination method to study the drying process of paints, based on digital holography and gravimetric measurement, is proposed. The proposed method allows taking holographic measurement in a simultaneous way to compare the results obtained by the reconstructed image changes with gravimetric data. By directly comparing a phase change in the reconstructed images of a paint surface and weight change of the paint film, it is found that a stationary state of the paint surface detected by the phase change occurs in the last stage of solvent evaporation and corresponds to a dry-hard of the paint film. The proposed technique can also analyze dryness of clear coat having no scattering particle using the phase change. It is shown that the present technique can allow us to further investigate not only a film formation of clear coat but also an estimation of specific gravity of solvents by comparing directly the phase change with weight loss due to solvent evaporation in the simultaneous measurement.