Ask the Expert Question-and-Answer Archive

by Ron Joseph

February, 2002

Measurement and Specification of Dry Film Thickness

Q. I'm not sure whether this is in your remit. Please can you advise the best (most durable and safest) coating (water based if possible) for the bath refinishing industry? And where to buy it? What I require for home refinishing involves spraying a new coating on vitreous enamel and ceramic porcelain. Also, I need a bonding agent to create a chemical bond between the new surface and coatings?

A. Dry film thickness is usually specified by the user, but guidelines for what a coating can achieve come from the paint vendor. There are no "standard" film thicknesses for specific coatings, but in many cases one can generalize. For instance, most decorative coatings can achieve a film thickness of 1.0 - 1.5 mils per application. Primers are often applied at 0.6 - 1.2 mils. Maintenance coatings can achieve film builds greater than 3 mils, even up to 8 mils in a single application.

It is common to specify not only the film thickness of the individual coats of a system, but also the total film thickness of the composite system.