Catalyzed varnishes, like other types of coatings, are composed of four main types of raw materials; resins, pigments, additives and solvents. All four are not needed to make a coating, but all four may be used. A better understanding of these four types of raw materials will provide the basis for additional knowledge of catalyzed varnish.

 

Resins are what provide most of the durability and what make the coating a catalyzed varnish instead of another coating type. The resin is the “clear” non-volatile (solid) portion that is left after the solvents evaporate. When we think of a coating film on a piece of furniture or cabinet we normally are thinking of the resins. They are what we are trying to apply to the woodwork to protect and beautify it. Some common resins in wood finishes are nitrocellulose, alkyds, acrylics, urethanes, amino resins (urea and melamine), cellulose acetate butyrate (CAB), vinyl, etc. If resins could do it alone, we wouldn’t need any of the other types of raw materials.

 

Pigments, also including dyes, can provide some durability and of course the color needed for some applications. Pigments and dyes allow us to create effects we would not otherwise be able to achieve. Many times it is these colors and effects of color that persuades the buyer to buy a particular piece of furniture or cabinet

 

Additives are a large group of raw materials that are put into the additive category based on: a small amount of the raw material has a significant impact on the properties of the coating and the raw material does not fit well into the other three categories. Additives can be used to improve the flow and leveling, slip and scratch resistance, cure time, color stability, UV stability, lessen settling, lessen foam, etc. Many finishers probably don’t even know how many or what types of additives might be in the coatings they use, but if the additives were left out the finisher would know the difference. A common additive finishers have used themselves is fisheye reducer.

 

Solvents are the final category. Most finishers are familiar with some solvents that they may add to the coatings themselves. The solvents are used to provide a way to efficiently and evenly apply the solids portions of the coating to the part in need of finish. Solvents have come under regulation in the United States and many other countries. It is important to note that some solvents are more hazardous to us and/or the environment than others. The most hazardous are being regulated to reduce or eliminate their use. This means that some of the common solvents of the past are being used at reduced levels or not used at all in coatings today. Regulations have been increasing and coatings are being reformulated constantly to meet the new regulations. Currently many coatings types, including catalyzed varnish, can be formulated to meet even the strict 275 grams per liter of Volatile Organic Compound limit in place in certain areas of the country.

 

Catalyzed varnish is a specific type of coating. The resin molecules are bonded together (cross-linked) when formulated, produced and applied properly. Two general categories of resins are used in catalyzed varnish formulations: polyol resins and amino resins. Polyol resins cross-link with amino resins at a high cross-link density, and that is what provides the great durability of catalyzed varnish. There are many types of polyol resins including:  alkyds, acrylics, vinyls, cellulose acetate butyrates, etc. The two types of amino resins commonly used are urea and melamine resins. Each type of resin has many varieties that allow a great range of possibilities when formulating catalyzed varnishes. The specifics of each resin used provide the specific characteristics of the cured film. Common properties provided by the choice of resin are: solids, clarity, chemical resistance, flexibility, cost, cure rate, pot-life, etc. A catalyzed varnish may have multiple polyol resins and amino resins blended to achieve the desired results.

 

Besides the resins, catalyzed varnishes need a catalyst to make the cross-linking happen. Catalyzed varnishes for wood typically use an acid catalyst. (Acids are not the only way to achieve cross-linking, high temperatures can also cross-link the resins without acid. However, the temperatures required would damage the wood substrate.) There are a variety of acids that will each provide different results. The specific acid and amount are chosen based on test results, so the recommended acid and amount provide the optimum balance of properties. Acids affect properties such as cure rate, pot-life, chemical resistance, flexibility, etc.