If you have been painting professionally for very long, you have no doubt come across a wide range of thickness gages. From interchemical gages to dry-film thickness gages, measurement of coating thickness both during and after a job is critical to your success as a professional. But knowing that a variety of different film thickness gages exist doesn’t necessarily mean you know which one is right for you and your paint team.
For example, the tools used for post-dry cross-section thickness testing are substantially different than the tools used for measurement before the coating cures. And those tools are quite different from the instruments required to measure film thickness after the paint has completely dried. Sometimes the different tools available can be so overwhelming as to make professional painters proceed without one at all. Talk about making a huge mistake!
If you’re confused about which gage is right for your purposes, let’s review the two most common wet film thickness gages so that you can easily understand how each performs and make a decision on which is best for the work you do.
To understand the importance of having a wet film thickness gage available to you while you work, it is important to differentiate between wet film thickness testing and dry film thickness testing. Simply put, wet film thickness measurement helps ensure that the job is being done right WHILE it’s happening, while dry film measurement ensures that the paint is behaving correctly before and after the job itself. Measuring a wet coating during a job is a great way to double-check the quality of your work so you can be sure the end result comes out as you expected.
As covered here before, the most common and inexpensive tool for thickness measurement is the wet film thickness gage. As the name implies, the tool is placed in wet paint for a quick and easy way to make sure a paint has been applied at the right thickness and has spread correctly. A wet film thickness gage isn’t likely to give you the same results as microscopic cross-sectional testing, but most of these wet film gages can measure to the micrometer and provide excellent results during a job. The cost of this tool is low-enough and the utility great enough that having one handy is an excellent idea, even if you don’t foresee using it on a regular basis.
A more expensive but more precise tool is the inmont film gage. Inmont film gages, like this one manufactured by BYK, are more accurate in their measurements and more versatile in their use. Using discs of different size and orientation within a roller provides more exact measurements. Even better, an inmont gage can measure coating thickness on curved and moving surfaces as well. The downside is that these gages are more expensive and require more rigorous cleaning then comb gages. If you use an IC gage, you will end up with more exact results but with higher cost and headache, so it’s not necessarily the best option if you aren’t going to need those kind of measurement with any regularity.
So what’s the right tool for you? Selecting the right type of wet film thickness gage depends a lot on the type of work you’ll be doing. Are you in a laboratory or out in the field? Is your substrate wood or glass, steel or plaster? Is it flat or curved? Are you working primarily in a controlled environment like a light room or painting the inside of houses? Or are you outside in the elements working in ever-changing and impossible-to-control conditions? The simpler your paint job, the simpler your instrument can be.