Paint Thickness Measurement on Drywall (Gypsum board)
DeFelsko manufactures a hand-held, non-destructive coating thickness gauge that is ideal for measuring the dry film thickness of paint applied to gypsum board (drywall).
Measurement Challenges
Drywall is typically painted with 3 layers (one primer and two paint). Traditionally a destructive test method is used to determine paint thickness. The primary challenge is to non-destructively measure the total thickness of the paint, typically in the range of 3 to 5 mils (75 –125 μm). Other challenges include a tendency for primer to absorb into the paper membrane of drywall, the effects of paint surface roughness or texturing, the impact of measuring over joint compound, and the potential need to measure individual paint or primer layers.
Dry Film Thickness Measurement Solution
The ultrasonic PosiTector 100 B gage is ideal for measuring the thickness of paint up to 20 mils (500 μm) on drywall. The instrument is capable of measuring total paint thickness on drywall without any adjustments right out-of-the-box. The gage’s large LCD display is capable of showing both numerical and graphical representations of the measurement. In the Screen Capture (Figure 1) shown below note that the graphical display clearly identifies the total paint thickness by showing the strongest return echo from the ultrasonic pulse. The instrument’s graphical display may provide additional information. In this example it indicates the amount of surface texturing, as well as absorption of the primer layer into the paper membrane.
Figure 1
When taking total thickness measurements, unusually high readings will be periodically yielded when the gage encounters joint compound covering the drywall seams. The resulting measurement would include the thickness of the joint compound in its total thickness calculation. This is due to a greater acoustic property differential between the drywall and joint compound, as compared to the joint compound and primer. By changing to a 2-layer application using the Setup menu, the gage will individually identify the total paint thickness and the joint compound thickness as shown in Figure 2.
Figure 2
The multi-layer measurement capability of the gage also has the potential to identify individual paint layer thickness, however this would be application specific since the gauge is limited by the differences in acoustic velocity between the primer and paint layers. As a minimum, layers could be individually measured as each paint layer is applied, allowing the user to calculate the thickness of the most recently applied layer.
The ultrasonic PosiTector 200 is a cost effective alternative for total thickness measurement of paint on drywall. The measurement range of the gage is 25 and 1000 microns (1 and 40 mils). The screen capture in Figure 3 represents the final of 10 readings taken with a PosiTector 200 in memory mode. The measurement location is the same as the PosiTector 100 result in Figure 1.
Free Consultation
For current pricing or to order these instruments, please contact us by telephone (315) 393-4450, fax (315) 393-8471, or e-mail techsale@defelsko.com. If you require additional technical information or have questions relating to your particular application, we encourage you to take advantage of our years of experience in recommending the best gage for your application.
Background on Paint on Drywall (Gypsum Board)
What is the Application?
The focus of this application is the ability to non-destructively measure paint thickness on gypsum board (more commonly referred to as drywall).
Why measure?
The primary purpose for measuring paint thickness on drywall is to control paint costs while ensuring adequate coverage. Commercial contracts often require an independent inspection of the work upon completion.
Where is the market?
Commercial contractors, painters and inspectors are the prime market for this application. Modular, sub division, and other high volume housing manufacturers are also potential markets.
Destructive Test Method Results
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Figure to the right shows an optically magnified cross-sectional image of the paper membrane and painted surface. Figure above shows reticule superimposed onto image. Units shown are in thousandths of an inch. Note that the natural paint thickness variation is between 3 and 5 mils (75 to 125 μm). |
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