07/09/2023
This is intended to be an informational guide for the different processes and products that Vintage Wood uses for interior wood finishing and furniture applications. Thanks to John Davis from Maclac who wrote the bones of this article
LACQUER COATING OVERVIEW
A (true) lacquer is defined as a coating that dries solely by the evaporation of solvents. As the solvents evaporate and leave the wet coat, the resins quickly form a dry "film" of lacquer. Therefore, since a lacquer dries by solvents leaving the coating, and no resin reaction takes place, the lacquer can be re-dissolved at any time in its own solvent (lacquer thinner). This is one of the reasons lacquers are so easy to work with. Application is easily adjusted with solvents, and the lacquer can be re-coated at any time with virtually no inter-coat adhesion problems. The new coat of lacquer will slightly re-dissolve or re-melt the previous coat and the two coats will bond strongly with each other. Neither "precatalyzed" nor "post catalyzed" lacquers, which are the two types of lacquer coatings that Vintage Wood uses, exactly fit this definition. These reacting lacquers will develop limited resistance to lacquer thinner solvents. Generally, post-catalyzed lacquers will have a higher degree of reactivity than the precatalyzed lacquers. True lacquers dry solely by evaporation of the solvents. When the solvents have evaporated the lacquer will achieve most of its performance properties. Both precatalyzed and post catalyzed lacquers will continue to cure after the initial air dry. The amount of additional cure is dependent upon the manufacturer’s formulation. The performance of any good lacquer coating is directly dependent on good application. If the lacquer has been properly applied it will achieve expected performance and durability.
The surface of wood is very porous. If you magnify the surface of wood you will see that it is full of "valleys and crevices". The insides of these pores and crevices contain pieces of wood fiber, particles of sanded wood, and dust or other debris. In order for a lacquer to adhere to the wood, it must be applied in such a way that the liquid coating will pe*****te into (or flow into) all the pores of the wood. It must also displace all the air from those areas, and it must stay wet enough to allow the air bubbles to come to the surface and leave the coating. In order for the lacquer to develop optimum adhesion it must "wet onto" the entire surface area - including any stain materials and fibers or dust. Proper wetting will ensure maximum bonding or adhesion of the lacquer to the wood. Additionally, the lacquer must be correctly applied so as to achieve correct dry film thickness. It is recommended that all coatings in the system be applied from the same lacquer “family”. It is not recommended to mix different technology coatings. Never mix a catalyzed curing system with a true lacquer drying system.
If a lacquer is applied properly with good flow it will wet the entire porous surface of the wood. If the lacquer is not applied with good flow and wetting - it will "bridge" across some of the pores. "Bridging" means that the lacquer has not flowed into the pore. Therefore, parts of the wood are not coated with lacquer. Areas where the lacquer has "bridged" will not be protected. Moisture will pe*****te under those "bridged" areas, and it will swell the wood (much like a sponge) and the swelling will break the coating loose. When the coating breaks loose from the wood it takes on a "white" or "milky" look. Particular care must be given to sharp corners, joints, and the porous “end grain” sections. Additionally, make sure the doors and any sections that are easily exposed to water are properly coated. The entire piece must receive sufficient coating to seal and protect.
PROPER MAINTENANCE
Assuming a cabinet has been well constructed with quality materials and properly coated with the correct coating system, then it must be maintained properly for long life. The owner must understand and follow recommended cleaning and maintenance of the finish in order to prevent damage to the wood. In addition to regular cleaning, any food spills must be cleaned up quickly. The most common problem associated with improper maintenance is water damage. This is due to excessive water exposure. Food build up can also hold moisture and food chemicals on the surface – thus contributing to problems. Usually accidental spills or too much water will run down the cabinet door and collect on the underside out of sight. Water will sit on the surface and with enough soaking time it can migrate under the finish where it soaks into the wood. Note that standing water – with enough time- can get through the finish through micro-pores, butt joints, sharp edges or other surface irregularity. Wood is a natural product that has an affinity for water. We are not aware of any commercially viable finishing system for wood that will allow it to achieve unlimited standing water resistance. A customized application of some coating systems that are applied with a complete understanding of all the mechanisms at work can achieve improved water resistance. However, once the water soaks into the wood (it won’t matter how tough the coating system is) the wood will swell up and break the coating loose. Those areas where the coating has broken loose will look white or milky. The lacquer or coating itself has not been directly damaged by water, but rather the coating has been broken loose due to the swelling action of the wood. It is the wood that has been damaged under the lacquer. Any foods or juice that get to the wood may accelerate the damage. When lacquers have been properly applied to wood, the wood surface becomes water resistant but NOT WATERPROOF – which means the surface will withstand temporary water exposures, but not long term water soaking. Any drops, puddles or standing water must be removed immediately. All parts of the cabinet must be dried with a soft cloth after cleaning. Lacquers are best cleaned with mild household cleaning agents. The waterborne cleaning solutions are the least aggressive. We have not found any adverse effects as long as the recommended cleaning directions are followed. After light application of cleaning agent it is essential to dry the area with a soft cloth. Use a “dabbing” motion rather than aggressive scrubbing. Excessive scrubbing can remove lacquer protection. For best results apply a wood treatment to the clean surface in order to improve water resistance. It is recommended you use a waterborne oil soap designed for wood surfaces. Another choice that works well is a lemon oil polish in a mineral spirits base. Both types will pe*****te well and give the surface water resistance. Always test a small area first to note any adverse reactions. Many wood cleaner products will both clean and polish. Do not use any abrasive-cleaning agents on these lacquer surfaces .
Microfiber cloths can be abrasive so cotton cloth is recommended for cleaning.
STAINS
Stains are used to bring color into the wood. They are generally applied (by spray, rag or brush) to properly prepared bare wood, and then wiped to a uniform appearance. The material that is left in the wood is the part that gives it the desired color. The amount of stain left in the wood affects both:
1) the color (tone or cast) and
2) the depth of color (its relative intensity)
GLAZES
A glaze is typically an accent color that is applied to a sealed or already coated surface. Glazes are usually applied by spray, brush or rag, and then they are wiped into the areas where color is desired. The glaze should not have any affect on the coating that it is applied onto. It should also stay wet long enough to move it to where it is desired, and to remove it from the areas where it is not desired. Some glazes may dry and form a paint-like finish. However most glazes do not dry to a strong finish, and they require a clear coat to seal and bond them to the previous coat. Most glazed systems are weakest at the glaze level, and if there is any film failure you can usually see it right at the glaze. The glaze will ALWAYS decrease the inter-coat adhesion of the coating system. The thicker the glaze has been applied then the more it will compromise the system.
Pigmented White and Color Lacquers
Pigmented lacquers apply and behave much like their clear counterparts. Thinning lacquers with lacquer thinner helps them wet the surface better and also helps the flow-out. In addition, the lacquer thinner in subsequent coats will partially “re-melt” the previous coat, which will give lacquers excellent inter-coat adhesion. Pigmented laquers can be formulated into any paint color. I use M.L Campbell Resistant which is a post catalyzed product.
CLEAR LACQUER
Precatalyzed lacquer systems such as M.L. Campbell Designr Select are in the water white category (no yellowing). Since precatalyzed lacquers dry by both solvent evaporation and a reaction between the resins, they offer higher durability and performance. Properly applied, these lacquers are suitable for the kitchen and bathroom environments. For greater performance, the catalyzed lacquer is hard to beat.
For superb performance conversion varnish such as M.L Campbell Klearvar is suggested but is quite a bit more expensive. This system does not fit the definition of a lacquer even though it is often applied as a lacquer. All the resins in the coating will react with each other as it cures. There is no air dry or lacquer type resins in the coating. Therefore the coating takes longer to dry and cure than a regular lacquer. After cure, conversion varnishes become resistant to most common chemicals. The conversion varnishes may have a slight amber color in the can – due to the nature of the resins but once applied they have very little tendency to yellow. These finishes are very water resistant, but they do not make wood waterproof.
