Experienced painters often dabble in mixing and matching products from different paint manufacturers, sometimes out of necessity to avoid wasting the materials that are already in the supply cabinet. Due to the sheer number of different products from the various paint companies, we can't even begin to touch on what will work with what. What we can say is that by sticking to a paint manufacturer's system of products, you can greatly reduce the variables and potential problems.
Application techniques for waterborne basecoats are similar to those of solvent basecoats, which helps to make the conversion process fairly painless. There are some differences though, so having a fundamental understanding of painting techniques along with common painting terms and methods will certainly help to understand the conversion process. It should be noted that the techniques that we will talk about here are specific for applying PPG's Envirobase HP waterborne basecoats. Application methods for other manufacturers' waterborne-based paints might be different. For instance, Ramos, who is also certified with the DuPont and Sikkens paint programs, explains that DuPont waterborne basecoats are applied wet on wet, whereas the PPG Envirobase HP base is applied when the previous coat has flashed to a dull, flat finish.
Although the toners in the Envirobase HP paint mixing system are formulated to give precise matches to OEM colors, there are certain steps to follow in order to get there. First is adequate coverage over the correct shade of sealer, which is accomplished with what PPG refers to as the "coverage coat." As mentioned earlier, the sealer must have adequate film thickness (but not too thick), and the shade must match PPG recommendations; the shade of the sealer ("shade" referring to darkness or lightness as opposed to hue) should match the base color as closely as possible (i.e., light-colored sealer for light colors and vice versa). Sufficient coverage over the sealer is attained when there is a uniform opacity; usually two coats. Distance from the surface during the coverage coat is 6 to 8 inches with an overlap of 75 percent. Air pressure is critical, but unlike solvent-based paint, each spray gun manufacturer has a specific air pressure recommendation.
Coverage and Control
Automobile manufacturers have been using waterborne paints for many years for the same reasons that the refinishing industry has been making the change: low VOC content and faster performance. The difference between the factory paint and that which is applied at a body and paint shop is that the OEM paint is applied electrostatically. When metallic colors are applied in this manner, the metallic particles or flakes are immediately locked in place by a static charge. Unfortunately, this is not possible when paints are applied on a refinishing level, so in addition to the coverage coat, metallic paints (as well as pearls and some special effects colors) require a "control coat." The control coat determines the accuracy of the color match and a uniform distribution of flakes that matches the factory finish. Without the electrostatic process, flake particles tend to sink with each layer of the coverage coat. The Envirobase HP control coat is what you might refer to as an "appearance coat." Properly applied with a consistent 80 to 90 percent overlap (Yes, 90 percent is almost a double-coat per pass!) at a distance of 10 to 12 inches and air pressure lowered by approximately 40 percent, the control coat keeps the flakes on top, rendering the same appearance as an OEM finish.