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Time really flies when you are having fun. I've been working in the professional woodworking industry for almost 30 years. My focus and enjoyment have revolved around the process of making wood look its best by using the finest finishes available in the industry.
Most of those finishes were solvent-based materials that negatively impact our environment. I will be the first to admit that I was certainly not worried about saving the owls and whales or anything else our environmental friends have been fighting to protect. The stark reality is that most industrial finishers today still do not have a lot of concern about how they impact the environment.
I recently spent several weeks training finishers in Southern California. The Southern California Air Quality Management District (SCAQMD) has imposed some of the most stringent regulations on volatile hazardous air pollutants (VHAP) and volatile organic compounds (VOC) of anywhere in the country. To meet the challenge of these regulations, the American Wood Finishing Institute devoted significant research to be prepared to provide solutions in Southern California.
At the beginning of the training event, AWFI surveyed the class on how many finishers used water-based coatings. None were currently using any significant volume of water-based coatings, and less than 20 percent of the attendees were willing to switch entirely to water-based products. This outlook was very surprising, particularly when the attendees expressed that they were willing to bring products across state lines and risk large fines if they were cited for using noncompliant coatings.
Why is there such a reluctance to use compliant materials, especially in California where it is assumed that all manufacturers are focused on "green" production and are forced to meet strict mandates to reduce greenhouse gas emissions?
In talking to different manufacturers and finishers, we learned there are many reasons why companies are failing to embrace compliant wood coating technologies in both solvent- and water-based formulations. Let's look at some of these issues:
- Both solvent- and water-based compliant coatings are priced much higher per gallon than conventional noncompliant technology.
- Compliant low VOC solvent-based coatings dry too quickly and are also considered difficult to apply. This results in a high rate of rework.
- Water-based coatings do not have the level of clarity equal to solvent-based coatings.
- Water-reducible coatings excessively raise the grain.
- Water-based materials don't atomize as well as other solvent-based coatings.
- Water-based coatings are susceptible to poor adhesion.
- Water-based materials are not as scratch-resistant as solvent-based materials.
- Dry time on water-based products is too long.
- Water-based coatings have more texture and don't have the smooth feel of solvent-based coatings.
- Water-based materials don't flush out and clean up easily.
- Water-based stains don't equal solvent-based stains in aesthetic appeal and workability.
Some of these concerns are valid, while other perceptions are not necessarily reality.
Let's take a look at each issue in depth.
Coating material cost
In most cases, it is true that the per gallon price of both compliant water-based and solvent-based materials may be higher than noncompliant materials. However, the comparable mil for mil square foot cost may not be higher than noncompliant coatings due to a higher spread rate and higher volume solids of the coating. In the case of water-based coatings, a reduction in facility insurance cost and waste disposal fees may offset the higher cost of the coatings.
Compliant solvent-based application problems
To formulate a compliant solvent-based material, coating manufacturers must remove solvents, such as Xylene and Toluene, which are on the HAPS (hazardous air pollutant) list and VOC list. Acetone is not listed as a VOC and, therefore, is an exempt solvent that can be used to replace noncompliant solvents. Some areas in California require coating manufacturers to formulate finishes that contain less than 2.75 lbs. per gal. of VOC per gallon. This requires a very high percent of acetone in the formula to meet these stringent requirements. Acetone evaporates at a rate of 14.4. Noncompliant solvents such as Xylene and Toluene have an evaporation rate of .086 and 1.8, respectively, thus causing stains and topcoats to dry too quickly, especially under high ambient temperatures.
To minimize this problem, air-assisted airless spray equipment should be used to apply these coatings. The lowest setting of atomization air should be used to keep the materials from drying too quickly during the application process. Normally, HVLP spray gun technology is not the choice of spray equipment to use because of excessive solvent evaporation during the application process. Often a small amount of slow retarder can be used to offset the fast evaporation of the acetone in the product.
Clarity of water-based coatings
Older formulations of water-based coatings often contributed to an undesirable bluish-white haze to the finish. Newer resin technology has greatly overcome this problem. Not all water-based coatings are created equally in this regard. Be sure to evaluate the material you have chosen over your darkest stain color to be sure you are satisfied with the clarity. Water-based coatings generally do not have the warm appearance of lacquer and other solvent-based clear coats. To work around this problem, a small amount of water-soluble dye color can be added to the clear coat to give a warm appearance.
Grain-raising with water-based materials
Some species of wood are susceptible to grain-raise and can be problematic with water-based coatings. Many newer water-based formulas are equal to solvent-based in minimizing the grain-raising of the wood. If you are experiencing excessive grain-raise, most likely the root cause is using the wrong process to sand and prepare the substrate in the whitewood sanding stage. Applying the finish by using the wrong application technique can also create problems with excessive grain-raise.
Spraying water-based materials
Water-based materials can be difficult to break up into small particle size in the atomization process. Normally, airless or air-assisted airless spray technology works best for water-based coatings. Water-based materials can be sensitive to shear. If you are using airless or air-assisted equipment, be sure that the equipment has an equally displacing pump and has a medium to large fluid section to minimize shear and micro foam.
Water-based adhesion
The adhesion properties of water-based coatings have improved dramatically over the original formulations first introduced into the industry. New resin technologies allow water-based coating to have the same or better adhesion qualities when compared side-by-side with the same category of solvent-based finishes. To achieve the proper adhesion, water-based coatings must be applied over properly prepared surfaces. Be sure to check with your manufacturer as to the final grit of abrasive you should use prior to applying the coating. Adhesion problems may occur if water-based finishes are applied over oil based wiping stains without sufficient dry times between the stain and clear coat.
Scratch resistance
It is generally accepted that water-based coatings are more susceptible to scratching than solvent-based materials. This is not always true, especially with the newer post-catalyzed, two-part formulations. It is our recommendation to check a variety of single- and two-component materials to choose the technology you are most comfortable with. For example, water-based UV cured materials will meet most any performance expectations and are generally much more durable than solvent-based coatings.
Water-based drying and curing
Cold substrate and coating materials will definitely cause the dry time of the coating to be dramatically extended. As with all coatings, it is best to spray water-based at a minimum of 72 degrees. Water-based coatings dry much quicker if an abundance of air is circulated in the drying area. The use of high velocity fans and halogen curing energy can accelerate the drying time of almost all water-based materials to between five to 10 minutes.
Water-based texture
Due to the high surface tension of water, many water-based materials do not dry as smoothly as solvent-based coatings. This problem can be minimized by taking extra care to thoroughly sand and condition the sealer coat before applying the final topcoat.
Flushing out water-based materials
Most finishers struggle with keeping their spray equipment clean when using water-based coatings. Once the material has dried and hardened in or on the equipment, water will not resoften the material, allowing the spray operator to thoroughly clean the equipment.
A minimal amount of frequent cleanup during the work shift will keep the material from hardening on the tips and exterior of the gun. It is best to entirely flush out the spray system each day, using an abundant amount of warm water. Always use stainless steel equipment when using water-based materials.
Water-based stains
Most water-based wiping stains do not provide the same level of workability and aesthetic appeal as oil-based stains. However, some of the new European technology is much more user-friendly, allowing the finisher to wipe it in the same manner as a wiping stain. On some species the appearance is very acceptable. Water-based "spray to color" stains have become very viable for a broad range of color and species of wood, and in some instances, they may be preferable to solvent-based stains.
Is water right for you?
Here is the big question: Should you be using water-based materials? Most often shops switch to water-based products when they are forced to by environmental agencies. If you are a smaller shop, you may not get inspected or cited for using noncompliant materials. However, within the next two to three years in California and other strict clean air regions of the country, enforcement officers will be inspecting large and small shops alike.
Don't wait until you are forced to comply overnight with your back up against the wall. Now is the time to research and develop processes to gradually transcend into compliant coating technologies.
There are also good reasons to look at water-based materials other than achieving compliance. Because of the new movie An Inconvenient Truth and increasing global attention on the environment, consumers are looking for "green" products. In large metropolitan areas, there is a trend for consumers to demand "green guard certified" products. Green guard certified products are selling at premium prices at double to triple the mark-up of noncertified products. For more information on Green guard certification, go to www.greenguard.org. Another compelling reason to go green is for fire safety in storage and application of nonflammable coatings.
Water-based coatings may not be for everyone. No one coating technology fits all production requirements. If you are not required to use low or no VOC coatings, you may not want to switch products overnight. However, as water-based and low VOC coating technology continues to improve, we recommend that you continue to look at the latest technologies. At some point, you may find that water-based coatings are a fit for your production requirements.
So jump into water, take a few laps and soon you may be swimming to success.
Ed. note: Phil Stevenson is the founder of the American Wood Finishing Institute in Vineland, N..J.
author: By Phil Stevenson