We’ve changed the way we paint cars: we are using water paints! Now these are not the streaky type of water paint you may have dabbled in when you were young. More correctly, we are using water-borne paints – paint solids mixed with water to make them fluid.
Automobile manufacturers have been switching over to water-borne paints for several years. The big push for this change has been environmental regulations designed to reduce VOC’s – volatile organic compounds – or as we simply call them, solvents. Solvents are mixed with the paints to make them fluid so they can be sprayed on the body panels, and painters refer to them as thinners or reducers, based on the chemical composition of the solvents. Now, body shops are becoming “greener” too by using water-borne paints.
Not all the paint materials used by a body shop are water-borne. Primers and fillers still use solvent-based carriers. The primer acts as a bonding agent between the bare metal and the colour coat. Fillers have more “body” to them, and fill slight low spots on the body panel. By sanding the panel after filler has been sprayed on it, the filler is removed from high spots but not the low spots, so the panel becomes smooth. Much of the difference between a quality paint finish and a so-so one is the time and quality of the workmanship spent getting those body panels smooth with filler. Even the best paints in the world look bad when sprayed on a wavy body panel.
Clear coats are sprayed on top of the paint colour coat to protect it and give it more depth. These clear coat finishes are also thinned with a solvent. The paint manufacturers have been working on new formulas to produce water-based clear coats, but few have matched the needed characteristics that solvent-based clear coats can provide. In the future, these too will probably be water-based.