Catalyzed Varnish 101 Greensboro NC

The relative ease of use and durability of catalyzed varnish has made it popular with wood finishers for decades. Catalyzed varnish holds up to just about any test for interior wood finishes. It is easy to apply and achieves the look customers want.

So, what makes catalyzed varnish perform the way it does?

A simple reaction of an alkyd resin with an amino resin in the presence of an acid is what makes it do what it does. We're not going to delve into textbook chemistry, just an overview of why it works so well and why sometimes it doesn't work so well.

Catalyzed varnish, like other coatings, are blends of chemicals that, when in the right proportions are mixed and applied properly, yield certain benefits. These chemicals can be divided into four main groups: resins, pigments, additives and solvents. Not all coatings have to have all four types of raw materials in them; it depends on what they are designed for.

Resins

Resins are normally what we think of when we think about the coating film. The resins are what determine the potential durability of the coating system. The resin is also something the end customer associates with value because it is something they actually get to see and touch.

Today there are a variety of resins used in wood coatings. Some of the most common are alkyd, amino (urea and melamine), oil, nitrocellulose, cellulose acetate butyrate (CAB), plasticizer (phthalate), acrylics, UV and polyurethane.

Pigments and dyes

Pigments and dyes are what add color or lower the sheen of the coating. Pigments can also add special effect looks, and some improve durability.

Imagine if there were no pigments and every piece of furniture just had clear coatings on. The colors and effects sometimes make the sale of a project, or make someone want to replace what they already have with something new. Pigments are also something the end customer considers valuable.

Additives

Additives encompass a wide variety of raw materials. The classification "additive" usually means a raw material used at a low percentage and has a noticeable effect on the characteristics of the coating.

Many times, additives are used by the coatings companies with finishers and end customers never knowing of their use. However, finishers and end customers do value the qualities additives bring to the coatings, even if they aren't aware of what caused those qualities.

Additives can be used to:

• Lessen settling of pigments
• Improve the flow and leveling of the coating at application
• Increase UV stability
• Disperse and stabilize the pigment for consistent color
• Alter the cure-rate
• Improve the scratch resistance

The list of what additives can be used for is almost endless. Some additives, such as fish-eye remover, are used by finishers. Just a little can make a big difference in the end result, but be careful not to over use as a little can be good, but too much is bad.

Solvents

Solvents, including water, are what allow finishers to move the other chemicals from the container to the furniture in an even and efficient way. After solvents evaporate their job is over. Solvents are chosen for their specific solvency (their strength or what they will dissolve), evaporation rate, regulatory approval and cost.

Many end customers don't realize the value the solvents have added to the coating because they don't get to see or touch them; however, they can indirectly see the benefits in a smooth coating.

Many solvent systems have been reformulated to comply with environmental regulations — and this will not stop as long as solvents are still in use. Some coatings, such as UV coatings, can be produced and applied without solvents.

Catalyzed varnish

Catalyzed varnish is a special type of coating. It cures by the cross-linking (bonding the molecules together) of alkyd and amino resins with acid as a catalyst to initiate the reaction. The high amount of cross-linking between the molecules is what makes catalyzed varnish so durable. The blend of toughness (hardness and flexibility) and chemical resistance makes them ideal for kitchen and bath cabinets, office and institutional furniture, and other interior wood applications requiring durability.

The specific alkyd and amino resins used along with the acid will determine the potential physical properties of the coating. Each of these raw materials will affect the coating's cure rate, pot-life, hardness, flexibility and chemical resistance.

Catalyzed varnish is used widely in the wood finishing industry because it's easier to use and cure than 2K polyurethane, plural component polyester and UV coatings. Simple application and good durability makes it popular. It's also more durable and available in higher solids than lacquers and pre- and post-catalyzed lacquers.

Proper use of catalyzed varnish

When adding the acid to a catalyzed varnish, it is very important to measure the acid correctly. Too little acid will slow the cure rate, and leave the varnish soft and less chemical-resistant. Too much acid will shorten the pot-life, cure too fast, and make it too brittle to withstand the expansion and contraction wood goes through during seasonal changes leading to cracked finish.

Most catalyzed varnishes have a same day pot-life. That means they need to be used within the same day as they are catalyzed. Check with the manufacturer for specific recommendations on pot-life.

Many catalyzed varnishes can be "decatalyzed" at the end of the day to save the leftover coating for next day use. Usually adding a greater than or equal amount of uncatalyzed varnish to the left over catalyzed varnish will reduce the acid concentration enough to lengthen the pot-life over night. The next day just add enough acid for the uncatalyzed varnish so it will cure properly. Check with the manufacturer for proper decatalyzing procedures.

Best application is usually 2 to 3 wet mil on vertical surfaces and 3 to 4 wet mil on horizontal surfaces. Less application leads to dry spray and poor flow because the solvents evaporate before the film flows out. More than that causes runs and sags, making the dry time too long and potentailly leading to over build of the finish. Overlap the spray pattern 50 percent to prevent streaks of glossy and flat areas and provide an even appearance.

Catalyzed finishes are also susceptible to lifting (wrinkling) of the finish. This usually occurs with the application and curing of the second coat of catalyzed finish over an uncatalyzed finish.

The uncatalyzed layer can be a catalyzed finish that did not catalyze fully, meaning not enough acid was used. Lifting can happen over spray stains, wiping stains and fillers if too much material is left on the part. Make sure uncatalyzed spray stains are not over applied under two or more coats of catalyzed finishes.

Make sure wiping stains and fillers are wiped off well, regularly replacing old wiping rags with new ones.

Catalyzed varnishes have proven their worth, and by continually learning about them they will meet the needs of many wood finishers into the future.

Ed. note: David Jackson began working for a wood coatings manufacturer in 1986 and has been formulating wood finishes since 1988. He held various titles including laboratory technician, formulator, senior chemist and general manager for two wood coatings companies. Jackson currently is the general manager for Jasper Chemical Coatings in Jasper, Ind.