What's In the Water?
Since waterborne paints are formulated in an acrylic latex resin base, they are water-soluble. The "water" in waterborne paint reducers consists of two parts hydrogen and one part oxygen ... that's right, H20, just like your standard everyday tap and drinking water, albeit in a purified form. Does this mean that you can simply turn the valve of your faucet and have an endless supply of inexpensive paint reducer and gun cleaner? Unfortunately no, although there are probably many who have done this and will swear that it works.
PPG offers two reducers for their Envirobase High Performance (EHP) waterborne basecoat paint. Like solvent-based reducers, recommendations are based on the temperature range in which the painter plans to paint. The standard EHP reducer is Number 494, and is recommended for use in temperatures ranging from cold up to 100 degrees with a relative humidity level of up to 30 percent. Number 494 should also be used if the relative humidity is above 30 percent, no matter the temperature. A slower reducer is EHP Number 595, which should be used only under extreme dry heat conditions over 100 degrees, and below 30 percent relative humidity. Unlike solvent reducers, which can be mixed and blended at the discretion of the painter, you cannot blend the two PPG waterborne reducers to create a mid-level reducer. You must select either 494 or 595 to reduce the Envirobase basecoat paint.
Perhaps the question most often asked by painters is, "Can you drink the water?" The answer, to be on the safe side, is that paint reducers are not intended for human consumption. If there is an active ingredient in the waterborne paint reducer, it is a chemical called butoxyethanol. While the name may be unfamiliar to you, this is simply an organic solvent that is commonly used as paint thinner and is also found in some ordinary off-the-shelf household cleaners. Butoxyethanol is non-toxic enough for the EPA to have removed it from its list of hazardous air pollutants over 15 years ago. Waterborne paint reducer has also undergone a process of purification known as de-ionization. Water that has been de-ionized will contain no significant traces of mineral ions that could adversely affect the paintjob. Using PPG's specially developed Envirobase reducers will minimize the possibility of contamination, de-lamination, discoloring, and rust spotting.
What Is A VOC?
We've established that waterborne automotive paints and undercoats are nothing new. However, it's more likely that the first water-based primers were introduced not necessarily to comply with VOC regulations, but to offer an option for the painter who was having compatibility problems with unknown undercoats and sensitive lacquer topcoats. Because a waterborne primer can effectively serve as a barrier coat between incompatible solvent-based products, painters have been using water-based undercoats for many years. For example, R-M (now BASF) first introduced an easy-sanding waterborne barrier coat back in the late '70s that, according to paint reps, allowed a fast-drying topcoat such as lacquer to be applied over fresh or uncatalyzed enamel without having to strip the surface. Due to its water base, VOC content was lower than that of solvent primers, but there was never any mention of the clean air emissions back then.
While the barrier effect is still a benefit of some waterborne coatings, the primary objective with today's paint is to reduce the emission of harmful solvents into the air that we breathe. In California, the agencies responsible for determining what is safe or not are the California Air Resources Board (CARB) and the Air Quality Management District (AQMD). On a federal level it is the Environmental Protection Agency (EPA). In light of all of the relearning that is now required in the painting industry, it's natural for painters to hold a little resentment to these agencies, but the bottom line is: they are only looking out for our better interests.