Interferometric monitoring of dip coating.

Dip-coated films, which are widely used in the coating industry, are usually measured by capacitive methods with micrometric precision. For the first time to our knowledge, we have applied an interferometric determination of the evolution of thickness in real time to nonvolatile Newtonian mineral oils with several viscosities and distinct dip withdrawing speeds. The evolution of film thickness during the process depends on time as t(-1/2), in accordance with a simple model. Comparison with measured results with an uncertainty of +/- 0.007 microm) showed good agreement after the initial steps of the process had been completed.