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As discussed in the introduction, Lacquer is a prime candidate to finish indoor furniture, especially in a small shop without a separate "clean room" for finishing, where long drying times require space and cleanliness not typically available. Lacquer is normally sprayed, but dries so fast that overspray is typically dry before it hits the floor - thus making it practical to spray without a dedicated spray booth.
Nitrocellulose lacquer, also called "traditional" lacquer, or solvent-based lacquer, stinks, literally, until it dries. It is a solvent based finish that forms a film by the evaporation of the solvent, not by a separate chemical reaction. The solvent in subsequent coats of the finish will cause the new coat to "melt into" or "burn into" the previous coats, leaving an integrated single layer of finish. As long as the solvent (thinner) is present, it remains a homogeneous liquid, so some people don't even clean the spray gun. It was used on General Motors cars from the 1920s through the 1950s, and is still often used as finger-nail polish.
Lacquer is made from wood (cellulose), dissolved in nitric acid and other lovely chemicals, and is not related to shellac (despite the similar names). The solvent in lacquer (lacquer thinner) is a flammable hydrocarbon (think gasoline). Californians call it illegal, chemists point out that after it evaporates from the finish, the solvent oxidizes, leaving byproducts that are similar to those from the fuel burned by our cars. It is not a flourocarbon like the air conditioning gasses that were destroying the atmosphere.
A couple points to scare you into being careful with traditional lacquer... but hopefully not to turn you away from this great finish. I know of a furniture repairman whose Northeast shop/barn (full of antiques being restored) burned to the ground after he sprayed some lacquer. I know a doctor who treated a Midwestern woodworker with third degree burns (charred flesh) from a lacquer fire. I know of a Texas furniture maker who sprayed in a well ventilated shop, finished, and closed up so it wouldn't be so cold while he cleaned up. They found his body in the shop the next day, suffocated from the fumes.
So why would I consider something this dangerous? Great finish, fast, easy to spray. It is so fast drying that few people can effectively brush it on. I live in Texas, so can spray outdoors most of the year. Lacquer dries so fast, that the overspray is dry before it hits the ground (you should even hold the spray gun closer to the work than you would with slower drying finishes). I often spray outdoors in the driveway, and stay at least 3-5 feet away from the cars - I have had no sign of overspray on either car. If you must spray indoors, beware of exhaust fans - motors cause sparks. Try blowing clean air into your spray area, and vent to the outside without blowers.
I have tried many tests to see if I could make lacquer fail. I have intentionally spilled wine, water, and other beverages on a lacquered surface, then set the glass in the spill (to keep it from evaporating) and after several days, have had no damage. I know that finger nail polish is often lacquer, so polish remover will remove lacquer from furniture as well. After years of feeling safe, I left a small lacquered piece near the kitchen sink. A few days later, there were spots in the finish. I have no idea what kitchen liquid caused the spots, but they did not come out. Maybe that is why the basic nitrocellulose lacquer is not recommended by the KCMA - Kitchen Cabinet Manufacturers Association.
Catalyzed lacquer has an extra chemical that gradually hardens the finish after it is applied. The initial coats still "burn in" creating a single integrated film, but over the next weeks and months, the finish becomes impervious to most solvents, and far less subject to damage. Lacquer may be pre-catalyzed (before you buy it), with a shelf life of months or even a year, and relatively slow hardening. You may mix the separate catalyst just before the lacquer is used, leaving the unmixed lacquer with an indefinite shelf life, and mixed catalyzed lacquer that must be used in hours or days, because it hardens rapidly.
Catalyzed lacquer is recommended by the KCMA for use in kitchens. It is used just like regular nitrocellulose lacquer.
Both uncatalyzed and catalyzed nitrocellulose lacquer are fairly thick as you buy it. Some people theorize that the lacquer is thick when it is sold so there is less solvent (lower percentage VOC - Volatile Organic Compounds), and the material appears less toxic. A top-of-the-line spray rig may be able to "atomize" the thick lacquer with little or no thinning. The instructions usually say "no need to thin" or they would have to include the thinner in the VOC rating. But most people find that a mix with 30-50% thinner works pretty well. If you thin too much, the finish may drool, and you may need more coats (the thinner doesn't add to the finish you are trying to "build"). But if it is too thick, the tiny droplets created by the spray gun may not be very small, and they may not flow together to make a smooth finish (often called orange peel, because the texture is like the skin of an orange). There is no perfect answer to the amount of thinner - it depends on the operator, the gun, the air supply, the temperature, the air pressure and volume in the gun, the paint volume, and perhaps the phase of the moon. If you are just starting, try 1/3 thinner - if the finish doesn't "flow smooth" add more thinner. If it works good, try less (thinner doesn't add to the finish, just to the cost and number of coats required). You will quickly become an expert.
Regular lacquer can be sprayed over a very wide range of temperatures. I have heard of people spraying below freezing, although I haven't worked that cold. I have sprayed with the work piece well over 100 degrees in the mid-day summer sun. But regular lacquer hates high humidity. As the solvent evaporates, the finish cools; if the humidity is high, moisture condenses into the finish, and leaves the surface milky. (Apply another coat of thin lacquer, when the humidity is down, and the problem should disappear.) One rule of thumb is that if even part of the sky is blue, the humidity is probably low enough. When evening comes and it starts to get dark, the humidity rises so you must quit. But one day I got up early when the sky was blue, and learned that the blue sky rule was just a guideline... don't start too early!
A "retarder" can be added to the lacquer (a few teaspoons per quart) to make it dry more slowly. This allows experts to brush the lacquer, and may allow you to spray when the humidity is higher (slower drying means it doesn't cool as much from the evaporation, so the moisture doesn't condense in the finish and turn it white). Some say the "Deft" brushing lacquer available from "retail" outlets is just regular lacquer with retarder.
In the 1950s chemists found that a synthetic acrylic resin could be used rather than cellulose, creating a more durable finish. Acrylic lacquer replaced nitrocellulose lacquer in the auto industry and other commercial shops starting in the 1950s, but required a multi-step finishing process. By the 1990s acrylic finishes became simple enough to become generally available, and in the past few years, have become both simpler and more durable. The current acrylic lacquers are water based... water is not the solvent, but when the water evaporates, the remaining chemicals react to form the finish.
I was quite happy with Nitrocellulose (solvent-based) lacquer. So it was a hard jump to a new finish. A number of my woodworking friends, all of whom recommended the same Target USL acrylic lacquer, finally convinced me to try. Within the first gallon, I was convinced, and have almost completely switched from Nitrocellulose Lacquer to Acrylic Lacquer. I did not switch because of concern for the environment (although that is nice), or because of fire safety (also nice), but because (to my surprise and delight) I get a better finish, easier.
There is little difference between brands of paint thinner or nitrocellulose lacquer or other solvent finishes. But you can't talk about water base finishes, including acrylic lacquer, without talking about a specific brand. The technology is still new enough that each brand has quite different characteristics.
I now use "Oxford" USL - Ulitma Spray Lacquer - from Target Coatings as my primary indoor furniture finish. It is more expensive than solvent lacquer (think over $10 per quart bought in large quantity), but the percent solids are higher, so it takes fewer coats. It doesn't require substantial thinning with lacquer thinner. It has full burn-in - which I think is unique (or at least rare) among water base products. That means that if you mess up rubbing out or sanding, and go through the layers, you do not get witness lines that identify each coat of finish. I have now used about 40-50 gallons of gloss USL (and one gallon of satin USL - see the page on sheen).
The gloss Target USL is really great to work with. It is self priming... you can use it on bare wood, like a sanding sealer. Arguably it may not bring out the color and grain as well as a coat of shellac or other first coat, and doesn't do quite as nice a job of filling open pore woods, but I still use it as the sealer for 90% of my work. I did a test with shellac primer on a scrap walnut plywood - half with shellac, half without - it was very hard to tell the difference after the Target USL was applied. Then I sand the first coat with a ROS - Random Orbital Sander, giving a perfectly level surface to build on. That sanding powders nicely, does not gum the sandpaper.
The build coats go on well... scary white in the can, but no problem spraying without thinning, and get a significant build per coat. As noted elsewhere, the outside back of a bookcase may not get anything after the first "prime" coat and a quick machine sanding to smooth any raised grain. The inside back of a bookcase, which gets no wear, may only get one build coat. The wear surfaces may get 3-4 build coats, depending on how good my technique is that day (If off, I spray thinner coats, and do more of them). With full burn-in, there are no witness lines between the coats - no problem whether I do fewer heavier coats or more thin coats. I don't sand between coats except to "ask for forgiveness" if I mess up, such as a drool. Just before the final coat, I quickly go over the surface by hand or ROS at 400 grit or finer, so that I have a perfectly smooth surface for the final coat.
If I need a satin finish, I machine sand 400, then 600, then rub quickly with a towel. (That satin is so nice, I have had a couple customers stroke the surface of a sample piece, put their face against it, and place an order if I promise to do the same for them.) For semi gloss, I may go to 800 before a quick rub with a towel. (The official recommendation is to wait a few days before rubbing, but I have had good results after only a few hours). Notice "machine sand"... this is really quick - not like the endless rubbing of nitrocellulose lacquer with steel wool. Don't use "real" steel wool on water-based finishes - tiny particles of steel may rust in the remaining moisture of the finish.
The exception to totally rubbing out a finish is a large piece (a set of bookcases or an entertainment center) with open grain wood like oak. Since I probably left the grain open, the recessed grain lines may be glossy when I rub the surface to a satin finish. In these cases, I do spray a final coat of satin USL, or use a synthetic wool (like the white 3M abrasive pads) to finish the finish.
For a high gloss, the finish is good just as sprayed (assuming the operator is having a good day). However, I got some Menzurna rubbing compounds/polishes - and got a near piano finish in no time at all, machine sanding to 800, then applying Menzurna with a pad on a ROS, then wiping clean, then the next Menzurna... I only used the first two of three available grits. ("2L" and "16"), and had a finish that was above the quality of the "gloss" finish from the gun, approaching the "grand piano" level of finish.
In my own use, I only spray the USL, but have friends who say it is also great as a brushing lacquer. I still use nitrocellulose lacquer on my turnings, since I can hold the application rag against the spinning piece and the warmth quickly evaporates the solvent and polishes the piece... the acrylic lacquer needs a chemical reaction to "cure" so it doesn't match my "rub it hot" technique.
I left my solvent lacquer in my spray gun... cleaned it every year or two. (The solvent keeps the lacquer dissolved, so no film forms in the gun. A gloss finish has no "grunge" that settles to the bottom.) A friend who uses pre-catalyzed lacquer leaves it in his gun, too, since he has enough volume that there is no problem reaching the shelf life of the lacquer while it is still in the gun.
Shellac can be sprayed or brushed. However, unlike lacquer, shellac has to be stirred before use. I have not been successful leaving shellac in a spray gun for long periods.
Unlike solvent lacquer, you are supposed to take water based finishes out of, and clean, the gun, after each use (I stretch that to at least daily). But the last time I checked, it took 90 seconds to clean a pressure feed HVLP gun... it cleans very easily with warm water in a sink - nothing like the horrors of cleaning latex paint. I expect I could clean my gravity feed gun in 30 seconds. An empty mustard squirt bottle helps force water through the feed tube and nozzle. Recently I forgot to clean the gun, and it worked fine the next day. And the next. Finally some of the dried lacquer from the inside of the paint cup started to plug the strainer. I'm back to cleaning daily, but it is fast and easy. I also found a solvent for dry acrylic lacquer at a commercial sprayer repair shop - nasty stuff (flammable, toxic), but it dissolves the drools that form on the gun and sink.
Target USL must be stirred well before use... there is no layer of heavy solids on the bottom of the can of gloss, but the many exotic chemicals in the finish have to be well mixed (I shake the gun if it has been sitting for a while). It doesn't stink or burn, but I would rather not breathe it, so still spray outside. Water isn't the solvent, but when the water evaporates, the chemicals left do their thing, and dry almost as fast as solvent lacquer. I have sprayed solvent lacquer when the work piece is in the summer sun (over 100 degrees), but cannot spray early/late in the day because of humidity. With Target USL, humidity is little or no problem, but it doesn't like the extreme heat of mid-day Texas. (I have pushed the limits on humidity, and can testify that it doesn't like to be rained on before it dries, but I have successfully sprayed outdoors late into the humid evening - until almost midnight, although it dries slower.)
I recommend moving the USL from the one or five gallon container to smaller containers, so it doesn't form a skin on the inside sides of the can (not surface skin, just finish on the container sides that doesn't stick to the coating inside the can). With some airtight juice containers (most juice containers are not airtight), I have had no skin, so I can just shake before filing the gun and spraying. In most cases, I don't even bother to strain any more. And a friend (who must be as cheap as me) points out that the strainers with the water based lacquer can be rinsed and reused.
Jerry Work (another retired computer guy turned woodworker) wrote a very informative 50 page manual on Target Coatings and related finishing techniques, see www.targetcoatings.com/manual.html
I have used USL on tables without problem, but I got a gallon of Target conversion varnish (EM-Tech 8000), which Jerry recommends for outdoor use like doors, or for extra hard counter/tabletops. It acted just like the USL - same spray technique. It doesn't claim to have burn-in, so I was careful to not rub through the top layer. It looked great, and in theory should be more durable on desktops and other wear surfaces.
After using it for years, I learned that regular nitrocellulose lacquer is not approved by KCMA - Kitchen cabinet manufacturer's association. In my tests, it wasn't damaged by wine, water, booze, soap, etc., but then had a piece that spent a few days next to the kitchen sink, and it had spots that wouldn't come out. I don't know what the spots were, but something that happened at the kitchen sink.
Catalyzed nitrocellulose lacquer is KCMA approved, so presumably is better than regular lacquer, but doesn't have the best test results.
Target USL lacquer is KCMA approved, and has very good KCMA test results - better than Catalyzed Lacquer. USL is an acrylic lacquer, not nitrocellulose, the successor product in the evolution of the chemical technology. By some chemical magic it burns into even totally dry acrylic lacquer (good), and apparently to some degree even burns into nitrocellulose lacquer (wow).
I refinished our breakfast table with USL to test it's durability. I scratch-sanded the underlying polyurethane for adhesion, and sprayed a couple coats of USL. It seemed soft for the first week or so, but is wearing well - stay tuned.
Nitrocellulose lacquer is quite generic - practically no difference between brands, except Deft reportedly contains a retarder to make it dry more slowly so it can be either sprayed or brushed.
Unfortunately Target Coatings are not available in your local big box or paint store. I started buying most of my Target from Jeff Jewitt (Homestead finishing) for two reasons... he had other things I needed, and if you are a customer you have access to Jeff (and Susan, his wife, partner, and co-author) for questions. Jeff doesn't carry all the Target products, so sometimes I order direct from Target - same price, same shipping cost, great service.
Good luck! Your comments and feedback are appreciated.
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