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Precatalyzed lacquers are widely used for their ease of use and repairability, while meeting the requirements of most furniture, cabinet and architectural woodwork. We can understand more about why pre-catalyzed lacquer works so well for a variety of applications by seeing how it came from a combination of lacquer and catalyzed varnish.

Lacquer is well known for its ease of use and great aesthetic qualities. It is generally acknowledged as the easiest to use and repair wood coating, and other coatings are often formulated to try to achieve the look of lacquer. Unfortunately lacquers are not as durable as many other types of coatings, such as catalyzed varnish, two-component polyurethane and UV.

Lacquer’s good properties and deficiencies are a result of the way the finish cures. Lacquer cures by solvent evaporation only. Once all the solvents have evaporated from the finish, the curing process is complete; no other curing mechanism takes place to enhance the durability of the coating. If other curing mechanisms are taking place in the lacquer, then it is not just a lacquer but a hybrid of different coating technologies. Various resins can be used in lacquers including: acrylic, nitrocellulose, cellulose acetate butyrate, alkyd, etc.

Each coat dissolves the previous coat and they flow together. This is why lacquer can look so good and repair so easily. Achieving a repair that is not visible requires less skill with lacquer than with other more durable types of coatings. However, the ability of the coating to dissolve also means that its durability is not as good as many applications require.

Catalyzed varnish is a very durable coating that can meet almost any interior wood coating requirement. This makes it popular when great durability is required. Catalyzed varnish cures by a reaction between alkyd and urea resins in the presence of a catalyst. Once the solvents have evaporated the alkyd and urea resins are left with the catalyst, and the reaction between the two resins takes place producing a “cross-linked” film. Cross-linking is the combining together of multiple molecules into one as if different pieces of metal are welded together. The cross-linking makes catalyzed varnishes very durable compared to lacquer. The catalyst is often an acid, so low temperature (room temperature) cure can take place. Heat could also be used as the catalyst, but with wood substrates it is impractical.

The way catalyzed varnish cures makes it very durable, but it also makes it more difficult to use. The proper catalyst must be added correctly according to the manufacturer’s recommendations and the pot-life is often one day or less. Pot-life is the length of time a catalyzed product is usable after the catalyst is added. Each coat of catalyzed varnish does not “melt” into the previous coat like lacquers do, so it shows more defects and is more difficult to repair aesthetically than lacquer.

Lifting is another common problem that must be avoided with catalyzed varnish. Lifting is a wrinkling of the coating that usually occurs when two coats of a catalyzed coating are applied over an uncatalyzed coating. Stains and glazes can act as the uncatalyzed coating if too much stain or glaze is left.