Just Finishing

Nitrocellulose Lacquer

The "old standby" finish by Michael Dresdner

Nitrocellulose lacquer has long been a favorite of wood finishers because of its beauty, case of spray application and repairability. In spite of increasing government regulations against its use, it is still one of the most widely used finishes for cabinctry and furniture.

Available in sheens ranging from high gloss to dead flat, lacquer forms a clear, slightly amber film that imparts great clarity and depth to wood. It is easy to apply and dries quickly. Unlike many oil varnishes and waterborne finishes, lacquer can be applied even in unfavorable conditions, such as high humidity, by adjusting its drying time with additives. It also has excellent rubbing-out characteristics and is easy to repair if damaged.

Like any finish, lacquer has its drawbacks. It's only moderately resistant to abrasion, alcohol, water and heat, so it isn't well suited to high-wear surfaces such as kitchen tabletops. And its toxic, flammable solvents demand health and safety precautions. Because the solvents are also air-polluting, government regulations restrict the use of lacquer by large manufacturers in many areas.

The Nature of Lacquer

Lacqucr forms a film solely by the evaporation of its solvents. Each coat rcdis-solves the previous coat, which means you don't have to sand between coats to ensure adhesion.

A coat of lacquer is so thin when dry—just a mil (0.001 in.) or two—that it hugs the wood, showing every detail and pore. If you want a closed-pore lacquer finish on open-pored woods, you'll have to apply pore filler first. (See 44Just Finishing," AW #27.)

Applying Lacquer

There are two ways to apply lacquer: with a brush and by spraying. Spraying is easier and generally results in a much better finish.

Brushing lacquer can be difficult because the finish often begins to dry before the brush marks level out.

Spray or brush. Nitrocellulose lacquer is easy to apply with a spray gun, though in damp, hot or cool conditions, you may need to alter its drying time by adding thinner or retarder. Lacquer made for brushing (right) dries more slowly.

Adding retarder to slow the drying time can help; I'll discuss that below. Or you can use a prcformulatcd, slow-drying lacqucr such as Deft,M (available at many paint stores).

Spraying is the best way to apply lacquer. Both conventional and HVLP guns work well. With a conventional gun, I spray at 30 psi (lbs. per sq. in.) air pressure, using a spray cap with a 0.070-in. (1.75mm) fluid hole. With an HVI.P gun, I prefer a smaller 0.050-in. (1.25mm) hole.

Caution: Lacquer and thinner are highly flammable. If spraying indoors, work in a well-ventilated spray room with explosion-proof fixtures. The fumes are also toxic, so wear a NIOSH-approved respirator when mixing and spraying the finish. Avoid breathing the fumes from the drying finish.

For your first coat on all but the densest woods, use a "sanding sealer"— a mixture of lacqucr and stcaratcs. Sanding sealer builds faster and sands easier than straight lacquer, but the stcaratcs arc soft and slightly opaque, so apply only one or two coats. Too thick a layer can invite chipping of the harder top coat and rob the finish of clarity.

Thin your lacquer or sealer to the consistency of skim milk, or even thinner if you're using a small touch-up gun. Stir the mixture thoroughly before spraying.

Spray each coat just thick enough to get the wood wet and shiny. Applying thicker coats may cause blush. discussed under Troubleshooting, below.

In ideal conditions—70° to 80" F and 40% relative humidity—lacquer dries to the touch in about 15 minutes and is ready to recoat within an hour or two. Even so, I recommend spraying no more than three coats per day. Plenty of drying time between coats keeps underlying coats from shrinking after the top coats cure.

You'll want at least four coats for a durable finish, but you can add more to get a thicker or flatter finish. Although lacquer doesn't require sanding between coats for adhesion, I sand with 220-grit 44self-lubricatingw (stearated) sandpaper between coats if there are any dust nibs.

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