Waterborne application techniques continue to change

Paint technology is ever changing, and to stay current, you must change with it. So what must we adapt to now?

We’ve learned in this industry that paint technology is ever changing, and as technology changes, we must change with it. Some of us who painted lacquer “back in the day” may remember the uproar posed by old-time painters as we changed to urethane and later to polyurethane paints. Those older painters had learned how to make the old paints work for them. They had learned to deal with the shrinkage, bull’s-eyes, polishing, and burn-throughs.

 As for those old timey enamel painters with their hot-plates for heating the paint before it was sprayed on the vehicle, they too found change difficult. In fact, I was hired because the painter I replaced refused to spray that “newfangled paint”. We grumbled through the change, spitting and swearing as we learned the new techniques. Now, as time has healed those old wounds, those of us who once used lacquer or old enamels wonder how we ever put up with them at all, and do not wish to return.

Start-up with Waterborne
So, what is the change we must adjust to now? Well, it is not really new. In fact, the first generation of waterborne paint technology was introduced into Europe in the early 1990’s, and before that the developers had been working on it for 20 years to develop a consistently usable product.  In the United States, the National Rule of 2008 regulated the amount of VOC's that coatings can have. Though many painters believe that this mandates waterborne coatings, it in fact regulates only the amount of VOC's in the coating. So if a solvent meets the requirement, it can be used.

Meanwhile, many paint companies, believing that the rule may become more stringent as pollutants continue to rise, worked on developing waterborne coatings which easy complied with the National Rule VOC requirements. In 2008 and 2009 parts of California were required to convert to waterborne paint. Then 2009 -2010, all of Canada changed as well. Other parts of the country, mostly in the east coast area, started the process in 2011-2012. Though there are large areas of the United States that have not mandated the switch to waterborne paint, many businesses have voluntary switched. Michigan, which has not mandated the switch, has one of the largest numbers of compliant shops in the nation.

So if a shop would like to change to waterborne paint, whether or not their state or region has mandated it, what must they do?  First they must consider the equipment changes. One of the most often asked questions is, “Will I need new spray booths and spray guns?” Though new spray booths will not be needed, some changes in drying/curing equipment may be. Most paint manufacturers recommend that a downdraft spray booth, which has the capacity to move large amounts of air, is the best type of booth to use; some booths may not move the needed amount of air for fast drying of waterborne finishes.

Traditional solvent-borne basecoats dry through evaporation, and though atmospheric humidity does affect the drying time of these finishes, temperature has a stronger influence on their curing time. Baking-type spray booths can significantly increase the cost of using solvent-borne paints. When waterborne paints are used, the cost of baking is markedly reduced. To speed up the cure time, a technician can choose a “faster” reducer and/or increase the temperature of the booth to reduce the coating’s cure time.

With waterborne finishes, air movement is what influences dry time the most, because water must evaporate from the finish. Though atmospheric humidity does influence the ability of a waterborne coating to evaporate, if air is moved rapidly over the surface of the painted vehicle, its evaporation is speeded up. Another phenomenon is that when water evaporates out of a finish, it increases the humidity of the air just above the painted surface. By circulating large amounts of air in the booth, the high humidity in this area just over the evaporating surface is moved and lower-humidity air takes its place, thus increasing drying.

Many booths that exist now may not move the needed amount of air, so to increase booth air movement special blowers called venturis may need to be added. Booths designed for waterborne finishes have venturis permanently installed (Fig 1). For existing booths, a movable venturi or venturis (Fig 2) can be placed in the booth, circulating air around the area on the vehicle which has been painted. 

One of the biggest enemies of a painter is dirt, and the natural question would be, “If all this air must be moved past fresh paint, isn’t it likely that dirt in the air would contaminate the fresh paint?” and the answer is yes. The air that is passed through the venturis must be scrupulously clean.

Another consideration may need addressing also. Though paper booth filters are not used much anymore, there are some booths that still use them. With all the water used with waterborne paints, paper filters can be damaged when used in conjunction with waterborne coatings.

Concerning spray guns, most spray guns being used today for solvent-based paints can also be used for the application of waterborne coatings. Though the technician must consider the recommended needle and nozzle sizes provided by paint manufacturers, gun cleanup may need to be altered. When traditional guns are used with waterborne paints, they should be cleaned with water first to remove the waterborne paint, and then rinsed with either solvent or alcohol to remove the water. Older guns have non-coated steel in them, which would be susceptible to corrosion when water only is used to clean them. Newer water-ready paint guns have stainless steel or coated parts which water does not affect, and water only can be used to clean the equipment.

Technicians now have specially-designed guns available for water application. These guns not only address the corrosion problem but also have addressed the gun’s ability to atomize waterborne paint. Shops that are contemplating switching to waterborne finishes may want to consider guns specifically designed for waterborne coating application.

Training
Though many paint companies will state that the switch to waterborne paint can be made easily, which is somewhat true, still making the switch is not without its learning curve. When the National Rule took effect, high-solids coatings became the standard. With the use of higher viscosity paints, more texture in the finish became a common side effect.  When water is the primary solvent, paint coatings are not restricted by the amount that can be added, thus letting technicians apply coating with little or no texture. Though high-solids solvent-borne clears are still needed to finish a refinish paint job, texture is much less a problem that it has been in the past.

Most paint manufacturers hold regular training classes for either new painters or to introduce new products to shops (Fig 3).

Paint and spray gun manufacturers continue to make products that lend themselves to the change with as little application technique change as possible. Technician training may still one of the best investments a shop can make, especially when changing to waterborne coatings.

Storage
With water as the principal solvent in waterborne coatings, freezing may become a problem. Transportation of product in the winter may require vehicles which have the ability to keep paint product from freezing. Storage at paint stores and in body shops also must be in heated areas to avoid freezing. Even when there is no danger of freezing, the paints need to be applied at suitable temperatures to avoid atomization and flow problems. In the winter paint may be shipped in insulated boxes to guard against freezing.

Reduction
A common misconception with waterborne coatings is that a paint shop can just take water from the tap to reduce the coating. Actually, the water used to reduce waterborne coatings must be de-ionized, and thus most companies recommend and supply the precise type of reducing water for their finishes. Any contaminant such as iron or other minerals in common tap water would cause undesirable side effects.

Safety
As mentioned earlier, waterborne coatings are much safer for the environment and the technician applying the coating. That is not to say that personal protective equipment will not be needed (Fig 4). Technicians must still read, understand, and follow all the safety precautions listed in the product MSDS. Paint manufacturers, in their quest to help paint shops reduce throughput cycle times, work continuously on developing safer coatings. Nonetheless, with the amount of hazardous ingredients they routinely are exposed to, paint technicians must be diligent in their pursuit of personal safety,

Latex vs. Urethane Waterborne
Waterborne paint technology is already changing and, I am sure, will continue to change as paint companies strive to improve their products. In fact, there are at present two different waterborne formulas in use today. One type of waterborne technology is a urethane paint that uses water as its principle solvent. The other is a true latex technology.  Manufacturers often recommend that these formulas be applied differently.

Tom Gardner of Pro-Spray paint states that their paint is a fourth generation waterborne paint. It is latex based "shake and pour" paint, which means that it does not need to be mechanically stirred by the mixing rack before pouring. The technician can just take the paint tint off the rack, gently agitate it by rocking or shaking it by hand; then the tint is ready to pour. For many, waterborne paint shelf life can be a concern, but Pro-Spray has a two year shelf life from the date of manufacture.  After the paint formula is mixed, the paint must be reduced by 10 to 15% with one of two special water reducers, one for normal painting conditions and a second for hot or low humidity areas.

Application of this latex is a two coat process with a control coat (as needed). The first coat is applied and then is dried with air amplification. Once the coat is dry, a second is applied. Many waterborne paints will have an off-color until the coat is fully dried and matted, so technicians shouldn’t get too worried until it is completely dry for proper color match.

One of the advantages when using this type of waterborne latex paint is that if the finish has a nib or other imperfection it does not need to be "washed off". You need just let it completely dry, and after it is "nibbed out" another coat is applied over the worked area to become undetectable.

Urethane waterborne paint uses urethane as the paint with water as the primary reducer. Many brands of these urethane waterbornes must be adjusted mechanically (Fig 5), just like their solvent counterparts. Though this type too needs large amounts of air to "dry" (Fig 6), the finish the application recommendation can be much different. The first coat is put on the panel, and with little or no flash time the second coat is applied to that panel. The surface is checked for complete coverage and a judgment is made for a third coat. After all the color is applied (Fig 7) the panel is air dried, but not between coats. The recommendation for panel progression is also different than others:  the panels that are to be painted completely are done first, and the blend areas are done after them. As always, it would be wise to check the particular paint maker’s recommendations and follow them.

Technicians will discover other advantages in using or switching to waterborne paint before regulations require us to.  First, cure time can be reduced, with the correct equipment, by using waterborne paints. Additionally, color match, metallic orientation, and blending can be enhanced with the use of waterborne basecoats; and technician safety is markedly increased when waterborne coatings are used. One of the myths about waterborne paints is that technicians need to use special respirators when applying water finishes, this fact is not supported in the product MSDS literature.

There are many reasons to convert to waterborne coatings, with the principal one being that in the future, shops will be required to convert. Next, using waterborne is significantly safer for the environment, and likewise for technicians. In addition, because the more expensive chemical solvents have been significantly reduced in waterborne paints, they may even be lower in price than “the old kind” as they become more popular.  With the proper time cycle, time can also be significantly reduced, when paired with fast cure time clearcoats. It is also significantly cheaper to operate venturis with compressed air than to operate paint booth bake ovens.

While waterborne conversion will become required, the requirement will also bring significant advantages for the industry, without significant adjustments or decreased profits.

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