Myths about Water Based Finishes

Myth #1-Lack Of Durability

Water-based finishes are significantly more durable than their solvent based counterparts in terms of mar, print and abrasion resistance. They are much more difficult to sand and remove from a wood surface than solvent based finishes. A typical finish remover will generally require more elbow grease to get them off. In fact, a water-based finish based on pure urethane cannot be removed with conventional removers. Only specially formulated, highly aggressive removers will take off such a finish.

Myth #2 - Lack Of Useful Life

Water-based finishes will outlast their solvent-based counterparts by as much as 300%, depending on type of product. For example, a water-based lacquer will outlast a conventional nitrocellulose lacquer by 5 to 10 years. A marine spar varnish will last only 4 to 5 months when subjected to Florida's hot sun and humid conditions. A marine type water-based polyurethane has a useful life of at least 12 months under the same weather conditions.

Myth #3 - Excessive Grain Raising

It is a fact that water-based finishes raise the grain from very slight to excessive. The degree of grain raising is a function of type of finish, manufacturer, type of wood, application temperature, drying time and, above all, smoothness of the sanded surfaces. It is important to point out that, contrary to false belief, some grain raising on the initial coat is necessary to a smooth and good looking finish. On the other hand, excessive grain raising is not good productivity wise.

Years ago, prior to the development of lacquer sanding sealers, it was a common practice to wet the wood with water in order to raise the grain, then the wood was sanded down to remove the dead fibers. Lacquer based sanding sealers were developed to achieve the same thing but with increased productivity. They were not designed however, for film building due to being soft and having poor water resistance. Lacquer based sanding sealers were designed to raise the grain then be sanded down to bare wood upon application. Their fast drying time was the key utility over wetting the wood surface with water.

Not all water based finishes raise the grain equally. The specific manufacturer and the finishes' drying time will dictate the degree of grain raising, all other factors being equal such as smoothness of the sanded surface. Smoothness of the sanded wood, which is a key factor, is discussed further.

The faster the drying time of a water-based finish the less grain raising will be experienced. A fast drying, spray type water-based lacquer will raise the grain minimally, similar to a nitrocellulose lacquer based sanding sealer. A slower drying, brushing type polyurethane will raise the grain more severely. Therefore, to minimize grain raising, a water based lacquer should be used and applied by spray. Applying a couple of light coats as initial coats, without sanding between the coats, will minimize grain raising as well. Applying a wet initial coat to raw or stained wood will raise the grain more severely. Degree of grain raising is inversely proportional to smoothness of the wood's surface. The smoother the sanded surface the less grain raising will be realized. Sanding the wood to only 120 grit will generate severe grain raising - sanding to 280 grit will generate none to very slight. On oak, ash, mahogany, poplar and walnut, grain raising can be eliminated or prevented by sanding to 280 grit. On cherry, maple and pine, grain raising can be eliminated or prevented by sanding to 220 grit.

It is important to mention that some water-based manufacturers now offer a wood Pre-Sea/product that eliminates grain raising and wood swelling completely. Such a product, though still water-based, employs unique resins that block grain raising and wood swelling provided the wood is sanded to 220 grit prior to application. In addition, most Wood Pre-Seal products also bring out warmth and color of the wood grain just like a solvent based lacquer. That is, on oak wood for instance, they bring out the yellow and red hues that are associated with warmth.

Finally, applying a cold product to a cold surface will cause the water to dwell on the surface hence cause grain raising. A warm product and a warm environment will cause the finish to dry faster thus minimizing or preventing grain raising.

Myth #4 - Difficult To Apply and/or Finicky To Use

With the advancing technology, water-based finishes are now as easy to apply as solvent based finishes provided proper spray equipment is utilized. Undersized spray equipment and/or applying a cold product to a cold surface will generate an orange peel. Following manufacturers label directions and published literature will yield excellent results.

Myth #5 - Clogging Of Spray Equipment

Some water-based finishes do clog spray equipment - most however, don't. In fact, some water-based lacquers on the market can now be left in the spray gun for days without the need to clean out - just like conventional nitrocellulose lacquer. Press the trigger and the product flows without spitting debris. This phenomenon is a result of a new chemistry developed over the last few years. Some of these newer water-based lacquers have a 100% burn-in, just like a nitrocellulose lacquer which prevents clogging and spitting.

Myth #6 - Sagging On Vertical Surfaces

Most water-based finishes can sag on vertical surfaces if applied too heavy - some however, don't. Sagging is a result of high specific gravity and gravitational pull. A water-based finish typically weighs 8.6 lbs/gal versus 7.6 for a solvent-based finish. The extra pound per gallon coupled with gravitational pull causes sagging to a very heavy coat applied. It should be mentioned that water-based finishes that have a 1 00% burn-in just like a nitrocellulose lacquer, should not sag on a vertical surface.

Myth #7. Extensive Drying Time

At 75 degrees F and 45 % relative humidity, water-based lacquers will dry to touch in 5 to 1 0 minutes. Only in a cool or cold environment and, high humidity will they dry significantly longer.

Myth #8 - Too Costly To Use

Gallon per gallon, water-based finishes are in fact more expensive than solvent based finishes. However, on a solids bases, water-based lacquers cost less than solvent-based lacquers. Solvent based lacquers on the average, cost 5.750 per square foot per mil versus 3.750 for water-based lacquers. This is due to at least 10% higher solids offered in a water-based lacquer versus nitrocellulose lacquer. Water-based polyurethanes are all around more expensive than solvent based counterparts. However, the added cost is well worth the price. Water-based polyurethanes dry 75% faster, last longer and most are UV stable which makes them very suitable for exterior application. That is, do not yellow over time.

Myth #9. Inflexible

Water-based finishes are very flexible yet very durable as well. Hit a solvent-based finish with a hammer on a wooden surface and it will crack or chip. Hit a water-based finish with a hammer and it will dent with the wood without cracking or chipping.

Myth #10 - Just As Bad For Your Health As A Solvent Based Finish

All water-based finishes do contain an organic solvent or a combination of solvents. However, the amounts are significantly less than in solvent based finishes, usually less than 1 0% by volume. Some water-based lacquers in fact contain less than 2% by volume. These solvents are an essential component for film formation known as coalescing solvents.

However, there are two important facts that need to be recognized regarding these solvents. One, these solvents are propylene glycol ether based and are not classified as hazardous substances by the EPA. Second, if these solvents are not propylene glycol ether based (ethylene due to cost), as these solvents evaporate, they are encapsulated by water that evaporates with them causing minimal health hazard.

Contact: rwolfe@acc-net.com
Hydrocote Finishing Products, Inc.
PO Box 207
112 Scioto St.
Green Camp, Ohio 43302
614-528-2150 Voice
800-866-7578 Voice (USA)
614-528-2437 Fax