All About Lacquers
For a century, the fine furniture featured in stores and catalogs, and now online, often boasted of sporting a lacquer finish. So it's understandable to think that because pros use it, lacquer must be the "best" finish. It can be—but not in every case and not without understanding the challenges that come with its application. Learn Why pros shoot lacquer, below, and the differences in the various products labeled as lacquer before deciding if this finish suits your next project.
So what is lacquer?
Lacquer gained favor in the 1920s as a finish that provided better protection and wear resistance than shellac, a favored finish of the era. Nitrocellulose (also referred to as NC or nitro) lacquer consists of cotton and cellulosic solids chemically modified with nitric acid and carried in a lacquer-thinner solvent. Like shellac, each coat of NC lacquer dissolves the previous coat, then dries again, to create one unified layer. This solvent-based finish still sees wide use today.
However, in response to concerns about air-polluting volatile organic compounds (VOCs) in the solvents that make up lacquer thinner, finish manufacturers developed water-based formulations that perform similarly to nitrocellulosic formulas—but there are differences.
Why pros shoot lacquer
Pros choose lacquer primarily because it dries fast, which allows them to build several coats in a short time and quickly move many pieces through the finishing process. Lacquer also provides moderate durability that suits a variety of indoor items, such as shelving, tables, and cabinets that won't see heavy use—so one finish works for many of a shop's builds. And should the finish need repair, most any solvent-based lacquer will melt into the existing coats, making fixes nearly invisible.
These shops cover surfaces quickly and evenly with high-volume, low-pressure (HVLP) spray equipment. Because lacquer generates flammable and unhealthy fumes that must be evacuated from the finishing area, pros spray in booths where explosion-proof fans pull a large volume of air through wall-size filters.
What you find on the shelf
In stores and online, you'll find many containers labeled "lacquer," but they are not all the same or interchangeable. Here's how to make sense of what you find.
If the label says the product requires lacquer thinner for thinning and cleanup, you have a solvent-based nitrocellulose lacquer, below. This finish imparts an amber tone to materials, it yellows with age, and it can become brittle. Exposure to sunlight can accelerate and increase yellowing and cracking or crazing.
A label that specifies water for cleanup indicates a water-based acrylic lacquer, above. This product goes on and stays clear, without the amber tone of solvent-based lacquer. Water-based formulations provide more flex, so are less likely to crack over time. The initial coat raises the wood grain, which requires sanding before recoating. Water-based lacquers contain fewer VOCs, and tend to cost more.
Curiosity about cats
Solvent-based lacquers can be found in two formulations: pre-catalyzed and post-catalyzed. Water-based lacquers may have a pre-catalyzed offering. Blending in a catalyst initiates a chemical reaction as the finish cures that makes the lacquer more durable—but at the expense of shelf life. Once the catalyst mixes with the lacquer, shelf life may be anywhere from 30 days to 2 years, depending on the formulation.
Precatalyzed lacquer (often referred to as pre-cat) has the catalyst added before (or just as) you buy it, (photo above, right). The minimum quantity may be a gallon, so consider whether you'll be able to use all or most of it before it expires.
Post-catalyzed lacquer (post-cat) is sold primarily to industrial and commercial users, so quantities begin at one gallon and go up. The catalyst comes separate and you must mix it into the lacquer before use. This allows for a longer shelf life for the uncatalyzed finish, and for mixing only the quantity needed. But mixing requires precision—otherwise the finish won't cure properly. Post-cat works well for pro users who buy finish in quantity and must ensure their supply stays viable until they need it. For home users, the hassle of buying larger quantities and then mixing smaller batches isn't worth it.
Laying down lacquer
Most lacquer gets sprayed using HVLP equipment, but other methods, below, don't require this investment. Regardless of how you apply it, the fumes for water- and solvent-based lacquers pose health and fire hazards—you must provide adequate ventilation. Protect yourself further with a respirator rated for organic vapors, and safety glasses.
Lacquer also requires a narrow window of temperature and humidity for best results: generally, between 65° and 85°F, with relative humidity below 65 percent. Too-humid or too-cool conditions can trap moisture below the finish as solvent flashes off, causing blushing, (photo, above).
Lacquer dries quickly for recoating, but allow 10 days before setting heavy items on a freshly finished surface. Cleaners containing ammonia, bleach, alcohol, or acetone will damage lacquer. Instead, use a damp rag or a spray-and-wipe furniture polish.
Because lacquer formulations vary among manufacturers, stick with the same brand and type (water- or solvent-based) once you start a job. If you have a repair job and don't know which type was used, generally, youcan apply a water-based lacquer over a solvent-based one. However, solvent-based over water-based may cause the existing finish to wrinkle. In either case, first test the combination in a hidden area.
Aerosol cans serve well for small projects where setup and cleanup would take longer than the finishing, but they cost the most per coverage area. Find ready-to-use rattle cans in just about every hardware store and home center. Satin, semi-gloss, and gloss sheens are common.
Most aerosols have fewer solids, and the nozzle dispenses smaller amounts than an HVLP gun, so apply more coats to reach the desired build. The narrow spray pattern reaches into small crevices and fine details without excessive build-up.
For covering large projects and vertical surfaces, a spray gun can't be beat. It provides the most control over how much finish you apply, by allowing you to thin the finish before spraying, and by adjusting the amount the gun dispenses. Like aerosol cans, a spray gun evenly covers detailed areas without finish building up in them.
You can get an HVLP gun to work with your air compressor without having to invest a lot. Be sure to use a water separator in your air line. Or step up to a self-contained HVLP system.
Brushing lacquer has additives that slow its drying time. This allows you to maintain a wet edge, but you must still work quickly. The higher solids content of brushing lacquer makes it more durable and helps it build thicker in fewer coats. However, higher solids make it a poor choice for repairs. For blending in fixes, choose an aerosol or thin and spray a standard lacquer.
Use a natural-bristle brush. Solvent-based and water-based lacquer will both melt a plastic or foam brush. Brushing lacquer can be thinned and sprayed, but because it dries slower, apply light coats to avoid runs and drips. You'll need to experiment to find how much thinner achieves the desired results.