Using Waterborne Paint - Hydrophobia

There's No Need to Fear Today's Line of Waterborne Paint

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It's been a long time coming, so we are really happy to finally be putting color on our '68 Camaro project car, Track Rat. Now, originally we were going to cover the car in a satin finish but found that the car would have looked great when first done, but it would have been all downhill from there. Get a scuff from a poorly placed cone and it's unlikely it will buff out. The same problem arises with environmental contaminants like bee pollen and gifts from our fine feathered friends. So we opted for something more durable, and that meant a traditional, high-gloss finish.

Back when we started this project, shops in California could still shoot solvent-based paints, but recent laws have forced them to switch over to waterborne paint systems. Like many new things, this change was met by apprehension from most shops. After all, most of the new "green" products out there might be better for planet Earth, but they tend to not work as well as their "dirtier" predecessors.

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The truth is waterborne paint isn't really new. The technology has been around a long time. Heck, Western Europe made the switch to waterborne over a decade ago, and over 60 percent of new automobiles come from the factory with waterborne basecoats. In the case of what we're using, Cromax Pro, it's Axalta Coating Systems (formerly DuPont Performance Coatings) third generation of waterborne paint.

There are two other things to note. First, today only the basecoat is water-based. The primers, sealers, and clears are all just as they've been for a long time: solvent-based. The second tidbit is that waterborne basecoats aren't all water. Water replaces a large part of the solvents, but some solvent (about 10 percent) remains in the paint. This mixture of water and solvents acts as a carrier to move the color from the spray gun to the surface of the car. The water and solvents then evaporate, leaving behind the pigments and resins that give a car its color. The processes and techniques employed between the two systems are very similar. It's just that one sheds far fewer volatile organic compounds (VOC) into the atmosphere, which are harmful to the environment. Specifically, water-based paints give off almost 90 percent less VOCs compared to solvent.

The main difference between solvent and water-based paints is how they evaporate. The key with solvent is temperature, while water is driven more by humidity. Because of this, airflow is the key to faster drying times. The irony here is that the older cross-draft booths are better than the newer downdraft type. The reason is that as the water evaporates from the paint surface, the air molecules near the surface become saturated and can't hold more water, slowing the process. If air is kept moving across the surface that is drying, the saturated air is constantly being replaced with fresh air.

The equipment needed to switch from solvent to waterborne paint is fairly minimal. Stainless-steel spray guns are not optional and fans can be used, but it really only speeds up the drying process. Also, make sure the compressed air is clean since oil and water are known not to play nice together.

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The Axalta paint we chose is quite a bit different from other waterborne paints on the market. First, it uses a wet-on-wet process rather than the typical coat-flash-coat method. Secondly, it has a higher solid content (the color that's left behind once all the other stuff evaporates) of 20 percent compared with 15 percent in other brands. This means that less paint has the ability to cover more car. Using less paint saves money on the supply side, and not having to wait for the paint to flash means money is saved on the labor side. Also, due to the higher solid content, coverage can be attained in as little as 1.5 coats compared to the 3-6 coats needed with other paints. This results in a thinner film coating that Axalta claims makes Cromax Pro more resistant to stone chips.

Best of Show Coach Works in Escondido, California, was forced to make the switch to waterborne paint over two years ago. At first they were a bit reluctant, but after working with the product, they've found it superior to solvent-based paints in many regards. They've also noticed that the colors seem more vibrant, which is a very good thing when you're spraying custom cars. The biggest issue is that it's somewhat harder to do repairs on cars shot with solvent since the waterborne paint shoots so much cleaner. But as time ticks by and more shops move to waterborne paint technology, this will become as uncommon as coming across a car shot in lacquer.

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