Why do we use a Lacquer or Acrylic Urethane Wood Finish & NOT a Paint Product on wood?
Wood is always breathing, expanding and contracting with the humidity changes in it's environment, any coatings applied should also have the ability to move with the wood as well as allowing the finish to breath. We all know how quickly the wood on a Deck can move and degrade, Outdoor conditions are the extreme, however the same factors are at play only on a smaller scale. The movement varies depending also on the type or species of the wood, the denser the wood the more movement there is. As wood expands and contracts the finish has to be flexible enough to move with it, should the finish/paint not be able to move as required fine cracks will begin to appear along wood grain patterns, this would be most evident when the wood is Oak as it shows a considerable amount of exposed grain. Eventually the moisture in the room will get into those cracks and begin to cause the paint to flake off. This can be accelerated when steam or moisture are present like in a bathroom, kitchen or Dining Room Table Tops.
I would say that Solid Oak Tables with the long open grain pattern and any end grain present are the most susceptible to this movement, wherever there is open grain patterns, knots or end grain present. These areas of the wood are the starting point for moisture absorption. The movement of moisture up into the grain is not unlike when a pan of water is placed under a cut Christmas Tree to slow the drying of the wood, it works the same way only on a smaller scale, it syphons the moisture, draws it in to the open pores. Furniture in the home has to deal with the humidity as it goes up and down, shower or cooking steam will increase that movement to some degree.
'Paints that dry by simple solvent evaporation and contain a solid binder dissolved in a solvent are known as lacquers. A solid film forms when the solvent evaporates, and because the film can re-dissolve in solvent, lacquers are not suitable for applications where high chemical resistance is needed. Classic nitrocellulose lacquers (oil based) fall into this category. The newer waterborne Acrylic Urethanes are much higher in moisture & chemical resistance and quickly becoming the standard finish for manufacturers due to the Low VOC content and fast drying ability they have.
Even the newer Waterborne Alkyd Urethane products made for wood Trim & Used on Kitchens by some are no match for a Lacquer, they simply do NOT level as well as lacquer meaning they are not as smooth. They get brittle over time and can't expand and contract like lacquer, the dry times between coatings are anywhere from 4 to 12 hours which makes the time to spray your kitchen far longer then needed and you are paying extra for that time!
Performance varies by formulation, however waterborne lacquers generally tend to have better UV resistance and lower corrosion resistance than comparable systems that cure by polymerization or coalescence (paint).
Latex paint is a water-borne dispersion of sub-micrometre polymer particles. Latex paints cure by a process called coalescence where first the water, and then the trace, or coalescing, solvent, evaporate and draw together and soften the latex binder particles and fuse them together into irreversibly bound networked structures, so that the paint will not redissolve in the solvent that originally carried it. The residual surfactants in paint as well as hydrolytic effects with some polymers cause the paint to remain susceptible to softening and, over time, degradation by water.' - Wikipedia
Lacquer is not unlike Nail polish, not just in it's chemical structure but in that it is made to be durable, chip resistant & is applied to a moving organic surface. Paint is made as a solid and can absorb moisture causing it to soften over time, it is unable to accommodate the movement of wood as good as Lacquers, Varnishes & Oils. Most Catalyzed Lacquers have a low life range of 15 years, with proper care this can easily go beyond that range. Paints have a 5 year range at which time they become brittle or soft if in high ,moisture areas. As paints get older they get less flexible. Latex Paints being susceptible to moisture create cleaning problems.
It is even possible for the wood on the underside of a solid wood table to draw in moisture and bring it right up and under the finish on the other side. If you have ever seen a piece of wood that has cupped itself and twisted, this is due to the varying degree of moisture that is in the wood, certain grain patterns allow for more movement then others.
The general rule of thumb is that it is always best to "Do to one Side, What you do to the Other Side", This is most important when dealing with solid woods. Veners/plywoods and proper construction techniques reduce the need to have equal finishes on both sides, however it is 'always best' to at least seal any exposed wood surfaces.
It is important to know what type and how much finish should be applied to the different wood furniture available, Lacquer is a wonderful wise choice when your looking for long lasting durability, a fine smooth finish along with resistance to chips and many household chemicals and beverages.
The Kitchen Cabinet Manufacturing Industry relies on Lacquers and do Not use paint for indoor wood finishing.
Nitro-Cellulose Oil Based Lacquers are highly volatile, considered Toxic and should only be used by Professionals in a Commercial Setting where proper ventilation is crucial. Never try to spray these lacquers in your home or garage. Notice the word 'Nitro' in the name, the glycerol ingredient found in nitroglyceren is used to make this type of lacquer. A spark can ignite the fumes or vapours quick and easy.
Read More About the Process: The biggest concern with lacquer is water resistance, whether hot or cold water. Various types of lacquers can be used depending on the circumstances, there are pre catalyzed or post catalyzed lacquers available whether they are oil, acrylic or low VOC water based. Lacquer is used on interior wood surfaces. There are what they call Automotive Lacquers available that are specifically made for use on metal intended for the outdoors, these offer complete sealing of the metal surface it is applied to.
Latex & Oil based Paint is thicker and can tend to build up in corners and grooves leaving areas that are not even. Lacquer is sprayed on in coats that are 2-3 mil in thickness, the end thickness is usually 4-6 mils. This provides a great bond and the ability for the wood to still breath through the finish. The finish looks thinner and professional, more so than a spray painted paint finish.
Lacquer also bonds to itself better then paint bonds to paint. This is helpful when one wants to update a colour on a lacquer finish. Lacquer when applied over lacquer has a softening or melting ability that allows it to fuse itself better, this tends to lead to a stronger finish that moves together along with the wood. Paint tends to layer itself more, this requires more sanding and primers in order to get good adhesion. We use lacquer sealers in substitute for primer and lacquer replaces paint.
We 'Spray Paint Kitchen Cabinets' making them look like new again, using long lasting lacquer equal or better to the original factory finish.
The DIY - Paint it at Home person can find some 'paint' spraying tips & techniques here: Furniture Paint Spraying Techniques Lacquer spray painting techniques vary by type, Water based lacquer's are more difficult to spray than Oil Based lacquer's.
Water Borne Lacquer or Acrylic Urethanes are heavy products so applying it to various styles of furniture varies considerably. Unlike paint, the tints can affect viscosity and the approach to spraying is crucial. Flat surfaces are considered to be straightforward (once you find the correct air to flow ratio, not all spraying guns are equal) A new approach is required wherever there are spindles, carvings, moldings or any area that requires using a different angle in order to get that even spray coverage , it takes a great deal of patience to spray these styles.
High traffic items or pieces that are near water or steam should stay away from paints, especially on solid woods, you have more flexibility when veneers are involved. Keep in mind that Lacquers tend to have a longer warranty period when applied according to the manufacturer's methods. My research shows that lacquer has 3.0 to 5 (times longer) warranty periods then the average name brand paints when used on wood furniture. 15 to 25 years depending on the type of lacquer and the method used to apply it. There are brushable lacquers available that can produce results as well.