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June 2021

How Hydrophobic are Hydrophobic Products?

In our April Newsletter, we featured part two of our Mary story.1 This time she goes to work in her Kia Cadenza with factory-treated hydrophobic windows. She also treated her car body with Shine Armor, a ceramic coating that promises to clean, shine, and protect. It's advertised as a hydrophobic top coat polish and sealant.

We ordered a bottle of Fortify Shine Armor to evaluate. We also ordered two competing products, Flowgenix Grand Finale Waterless Car Wash Shine and Shield, and Auto Fanatic 007 Gloss Enhancer. All three of these products are advertised to make your car body more hydrophobic are are safe and effective to use on any exterior surface - painted panels, glass, plastic and chrome trim. This month, we set out to determine how hydrophobic these products really are. After all, that's our business, to measure contact angle and wetting behavior.

We chose three different surfaces for our testing - a painted metal surface, a glass surface, and a plastic polymer surface. These represented the three most common surfaces on the body of a car. Three coupons for each surface type were cleaned and then we measured the contact angle on the untreated test surfaces. We then followed the manufacturer's recommended application instructions and applied the coatings to the surfaces. We then measured the the contact angle on the treated surfaces. For each coupon, we took three measurements on three unique drops. Each measurement reported below is the mean of the left and right contact angles for all three measurements for each solid/liquid combination.

The first and most surprising discovery was that for the painted surface - which represents over 90% of a car's body actually showed a drop in contact angle after application of the coatings. The table below reports our measurements:

Painted Surface      
Coupon ID Untreated CA Treatment Treated CA Delta
A 88.82° Shine Armor 73.03° -17.78%
B 87.00° Flowgenix 76.55° -12.01%
C 91.06° Auto Fanatic 71.77° -21.18%

As you can see, the mean contact angle actually decreased as a result of the surface treatments. The contact angle was driven lower by the treatments between 12% and 21%. This is contrary to our anticipated expectation and came as a surprise. In fairness to these products, the coatings are designed to be applied to a clear coat. Our samples were painted but not clear coated. Nor were they previously polished.

So, we did a real world test and applied each coating the various panels of my Ford Mustang GT, pictured below.

After application, we did notice that the coated sections appeared very similar to each other. Each produced a somewhat glossier and shiny surface. However, after wetting the surface, we noticed no real difference between the treated panels and the untreated panels - in terms of wetting behavior. Nor did we notice any difference between the three panels treated with the three test products.

So, at this point, we observe that all three of these surface treatments will bring a shine to a car body but do little to actually improve hydrophobicity. And on our test samples, the surfaces became less hydrophobic after treatement.

Next, we conducted the same test on glass samples. Below are the results:

Glass Surface      
Coupon ID Untreated CA Treatment Treated CA Delta
A 45.87° Shine Armor 46.04° 0.37%
B 48.89° Flowgenix 43.64° -10.74%
C 49.31° Auto Fanatic 64.69° 31.19%

The Shine Armor appeared to have virtually no effect on the wetting properties of the surface. The Flowgenix coating increased wetting by nearly 11%. Only the Auto Fanatic coating shown an increase in contact angle - over 30% in fact.

Our last test was on smooth plastic. All three products are reported to work on any car surface. Our results are summarized in this table:

Plastic Surface      
Coupon ID Untreated CA Treatment Treated CA Delta
A 73.46° Shine Armor 83.89° 14.20%
B 75.22° Flowgenix 81.31° 8.10%
C 74.49° Auto Fanatic 65.01° -12.73%

Contact angle increased with both Shine Armor and the Flowgenix products - but not by that much. The contact angle actually decreased for Auto Fanatic coating.

So, what do we make of these products? While they do bring a shine to a car's exterior body surfaces, our extensive testing and observations conclude that none of these products do much in the way of improving hydrophobicity. After our testing, we found that our results were not that much different from other testers of these products.2 

The moral of the story is: just because someone promises to make your car body (or anything else) more hydrophobic, don't take their word for it. Test it for yourself with a ramé-hart contact angle goniometer and you might be as surprised as we were this month.

1 If you missed it, you can read it here.
See this review video and this video.

How the ramé-hart Calibration Works
Every ramé-hart instrument must be calibrated in order take precise and accurate measurements. We've developed videos that show how to perform a calibration.1 If an instrument is calibrated properly, the aspect ratio will be very close to 1.0000. Here's how it works: It starts with our Precision Combo Calibration Device which is included with every instrument we sell. On the calibration tool, there is a precision 4mm ball that is mounted on a Plexiglas pain. We place the calibration tool on the instrument's specimen stage and then we focus and take a picture. DROPimage will then precisely measure the width and height of the sphere in pixels. Then, knowing the diameter of the sphere, DROPimage calculates the size of a single pixel in both horizontal and vertical directions and reports and records that value in microns to three places. Once calibrated, all subsequent linear and angular measurements reference back to the current values stored from the most recent calibration. It's not necessary to re-calibrate your instrument on a daily basis, but it is a good idea to check the calibration daily just to ensure that nothing has changed. Only if there is a significant difference between the stored values and the new values should a new calibration be performed.

1 For DROPimage CA, see this video. For DROPimage Pro (and Standard), see this one. And for DROPimage Advanced, see this one.

Carl Clegg
Director of Sales
Phone 973-448-0305
Contact us


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