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Furniture finishing techniques
Lacquer

Overview

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. Long drying times of many other finishes require space and cleanliness not typically available in a small shop. Lacquer is normally sprayed, but dries so fast that overspray is typically dry before it hits the floor - thus making it practical to spray clear finishes without a dedicated spray booth (clear so the dry "powder" doesn't leave a color on the driveway or deck).

Although nitrocellulose lacquer is becoming obsolete, and has been outlawed or restricted in many jurisdictions, understanding it helps put the newer finishes in perspective. But if you are impatient, you can jump ahead to the acrylic lacquer that I now recommend.

Traditional Nitrocellulose Lacquer

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 fluorocarbon like the air conditioning gasses that were destroying the ozone layer of the atmosphere. Nevertheless it is gradually being outlawed.

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. A leaky spray can of insect repellant damaged one customer's table - as a chemist explained, the active ingredient "Deet" is an extremely harsh chemical. After years of feeling safe except for these harsh chemicals, 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 Nitrocellulose Lacquer

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 cures more rapidly. Like uncatalyzed lacquer, it is flammable, toxic, and likely to be outlawed.

Catalyzed lacquer is recommended by the KCMA for use in kitchens. It is used just like regular nitrocellulose lacquer - the extra hardening occurs in the days or weeks after the finish is complete.

Use of traditional 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 fluid 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 - called blush. (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.

Acrylic lacquer

In the 1950s chemists found that a synthetic acrylic resin could be used rather than cellulose (wood), 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 keeps the other chemicals from reacting. 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 brand 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), or the less toxic fumes (nice), but because (to my surprise and delight) I get a better finish, easier. This is a very forgiving, easy to use finish.

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.

For several years I used "Oxford" USL - Ultima Spray Lacquer - from Target Coatings as my primary indoor furniture finish. It is more expensive than solvent lacquer (think over $10 per quart when bought in large quantity, and as much as $30 per quart bought by the single quart), but the percent solids are higher, so it takes fewer coats. It doesn't require substantial thinning with an expensive lacquer thinner. It has full burn-in - which is unique among water base lacquers (If you find another water based lacquer with burn-in, please let me know). That means that if you rub out or sand the finish, you do not get witness lines as you go through the layers. I have used over 50 gallons of gloss USL (and one gallon of satin USL - see the page on sheen), and continue to love it.

Target Coatings has come out with an improved version, the next generation of the same product, EmTech 6000 Production Lacquer (as of April 1, 2009, they no longer produce USL). I have done quite a bit of research, including talking with Jeff Weiss, the inventor, and am confident in the new product. The adhesion has been enhanced so it now works with multimedia items that include metal, PVC, carbon fiber, etc. You can use USL and EM-6000 on the same project, in the same way, and it is close enough that you can mix the remnants of USL, in a spray gun, with the new EM-6000 (stir well). I have already used over 50 gallons of EM-6000.

The gloss Target Lacquer is really great to work with. It is self priming... you can use it on bare wood, like a sanding sealer (you may want to dilute the first coat or two with a small amount of water to help fill the pores). It may not bring out the color and grain as well as a coat of shellac or other first coat, and at full thickness doesn't do quite as nice a job of filling open pore woods. Therefore I now primarily use Target EM1000 sealer to seal the pores and bring out the natural color of the wood. (If I need a barrier coat over previous finishes, I use solvent based shellac). Then I sand the first coat(s) with a ROS - Random Orbital Sander, typically at 400 grit, giving a perfectly level surface to build on.

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 after sealing. The wear surfaces may get 3-4 build coats, depending on how good my technique is that day (If my performance is 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 too heavy spray that leads to 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 to receive the final coat.

If I need a satin finish, I machine sand the gloss finish to 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 sand the gloss to 800 grit or finer before a quick rub with a towel. If you are dry sanding, you can proceed after a few hours, but if you are going to wet sand, as you might prefer with finer grits, you need to wait for the finish to cure - up to 120 hours at 70 degrees. Notice "machine sand"... this is really quick - not like the endless rubbing of nitrocellulose lacquer with steel wool.

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 (no grain filler), the recessed grain lines may still be glossy when I rub the surface to a satin finish. In these cases, I do spray a final coat of satin or semi-gloss lacquer, or use a synthetic wool (like the white 3M abrasive pads) to finish the finish - the synthetic pads reach into the grain to make the sheen even.

For a high gloss, the finish is good just as sprayed (assuming the operator is having a good day). However, I have used some Menzerna rubbing compounds/polishes - and got a near piano finish in no time at all, machine sanding to 800, then applying Menzerna with a pad on a ROS, then wiping clean, then the next Menzerna. Normally 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. If I were going for the ultimate "grand piano" level of finish I would continue with the Menzerna Intensive Polish.

Target coatings has come out with a new EM-7000 High Build Lacquer, which presumably will need fewer coats to build the finish. Multiple coats of EM-6000 are so easy to me, that I haven't rushed to try the new high build finish.

In my own use, I only spray the acrylic lacquer, but have friends who say it is also great as a brushing lacquer. (If you brush, you need to be skilled and have a very good brush.) I still use nitrocellulose lacquer on my lathe 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 and it is done" technique.

For a detailed list of the Target Coatings I "stock" see Target

Zingers

Never use "real" steel wool with any water base finishes - tiny particles of steel embed in the finish and may rust in the remaining moisture of the finish, or when later coats are applied.

Avoid the 3M coarse maroon synthetic wool, which I hear sometimes bleeds color. I have not had a problem with the Mirka maroon synthetic abrasive, where the color is just a code for the grit, rather than the color of the abrasive itself.

I got a note from someone who had problems spraying black finish in the hot sun. Apparently the black absorbed the heat, and caused the top layer of finish to dry (skin over) before the lower layers dried, thus with the extreme heat, blisters formed in the finish. I know walnut, in the sun, can get too hot to handle, and I expect black would be even hotter.

Some people have had problems using water based finishes over solvent based stains or finishes. I have not, but I do make sure the underlying finish is completely dry, and sanded for adhesion. I have heard concern about using the latest version of Zinsser Seal Coat under water based finishes - but dewaxed shellac made from flakes is presumably okay. I have not had a problem with Seal Coat.

Cleanup

Solvent-based Nitrocellulose Lacquer

I left my gloss 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

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. I do keep a dedicated brush in my "working" jar of dilute shellac. I have also found shellac so hard to clean that I have dedicated a cheap spray gun to shellac. The alcohol in the new shellac softens the imperfectly cleaned old shellac, but no amount of solvent or effort seems to completely clean shellac out of brush or gun.

Acrylic Lacquer

Unlike solvent lacquer, you are supposed to take water based finishes out of, and clean, the gun, after each use (I stretch that to cleaning daily or at least every few days). 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. A wooden toothpick to clean the nozzle is worth the few seconds it takes to remove the nozzle. 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.

I recently found a recommendation that may be helpful. My primary (turbine) HVLP gun does not have tiny air holes, but my gravity feed conversion HVLP gun has 10 very tiny air holes. Those holes occasionally get plugged and are difficult to keep clean. The recommendation was to clean the gun, then store the air cap (with the precision tiny holes) in denatured alcohol - which presumably will keep those holes clear. Testing shows that denatured alcohol will soften and remove the dry-to-the-touch but un-cured acrylic lacquer. So far, I like the idea.

Logistics

Any semi-gloss or satin finish must be thoroughly stirred, and must be kept stirred during use, or the solids that reduce the gloss will settle. Gloss finishes don't have the heavy solids, but a modest stirring is advisable to be sure the many exotic chemicals in the modern finishes are well mixed. I swish the spray gun if it has been sitting for a while, even with gloss.

Target coatings, and most other water base products, don't stink or burn, but I would rather not breathe them, so I still normally spray outside. Water isn't the solvent, so it won't dissolve the finish, but when the water evaporates, the chemicals left do their thing, and dry to the touch 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 acrylic lacquer, humidity has proven to be little or no problem, but it doesn't like the extreme heat of mid-day Texas. (I have pushed the limits on humidity, to the point that I have learned 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 more slowly in high humidity.)

797I recommend moving the finish from the larger one or five gallon container to smaller containers. It doesn't form a surface skin, but dry finish on the inside sides of the container sometimes comes loose and can cause problems in the spray gun. Most plastic juice containers are not airtight, but I have found some inexpensive two quart containers that are airtight, form no skin, so I can just shake quickly before filling the spray gun. In most cases, I don't even bother to strain any more, although that is always a good practice. And a friend (who must be as cheap as me) points out that you will probably rinse the strainers before discarding, and if you rinse, then when it is dry it can be reused. (I had one "disposable" strainer that lasted a year). When I am done spraying for the day, the finish left in the gun is always put into a separate container (a jelly jar with screw top) so that I am certain that the finish in the primary containers is not contaminated.

Several years ago Jerry Work (another retired computer guy turned full-time woodworker) wrote a very informative 50 page manual on Target Coatings and related finishing techniques, now available on his web site - see www.jerrywork.com. If you have trouble, drop me a note, and I will mail you a copy (over 2 MB).

I have used the regular acrylic lacquer on table and desk work surfaces without problem, and after it has cured for a week or so, it wears well (one specification for a full chemical cure is 100 hours between 60 and 80 degrees, another says 120 hours - 5 days - at 70 degrees). I got a gallon of Target conversion varnish (EM-Tech 8000cv), which Jerry recommends for outdoor use like doors, or for extra hard counter/tabletops. It went on just like the lacquer - same spray technique. It doesn't have burn-in, so I was careful to not rub through the top layer. It looked great, and appears to be more durable on desktops and other high wear surfaces. The shelf life of the EM-8000 is nominally a year, (it really doesn't work well when it is too old), so don't stock up too much. The EM-6000 lacquer has a comfortably long shelf life.

A few years ago I got some Target EM9300 polycarbonate finish, for a counter in an auto repair shop. After three years of keys sliding over the counter all day, I could not see any wear. I am now starting to use EM9300 when I need a very hard surface.

Durability

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 small 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 lacquer is KCMA approved, and has very good KCMA test results - better in most tests than Catalyzed Lacquer. EM-6000 is 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 cured 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, as expected, but showed no wear after several years. Some local vendors begged me to try a competing product from Fuhr, so my breakfast table was again the test dummy. As noted below, I gave most of the gallon of Fuhr finish away, and have since sanded the unsatisfactory Fuhr finish off and refinished with Target EM-8000 Conversion Varnish (another test).

Availability

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 know people who have missed the opportunity to try it because they weren't willing to buy finish by mail order. (I urge you to start asking for it at woodworking stores like Woodcraft and Rockler). As I already noted, numerous friends talked me into trying Target coatings. Once I tried it, I was hooked. I order direct from Target - great service, frequent special sales, and access to Jeff Weiss, owner and inventor of the Target products.

Competition:

I have tried MinWax Polycrylic water base acrylic finish, and my reaction was to return to nitrocellulose lacquer. The finish is okay, the durability seems okay. Minwax recommends that you sand between coats for adhesion, so obviously there is no burn-in between layers (dangerous if you are going to rub out the finish). It is nowhere near as easy to use, as forgiving, or as nice a result as Target. Our coffee table was a test piece for Polycrylic, and I hated the appearance of the table for 10 of the 11 years before I finally sanded it off and refinished it with Target finishes. MinWax is made by Sherwin Williams, and is available through the big box (Home Depot, Lowes, etc.) stores.

I spoke to General Finishes at AWFS in 2007. The booth babes couldn't answer technical questions such as burn in and cure time before rub out, so after the show, they had their tech expert contact me. They have several water-based finishes, but his answer was "of course it does" to everything I asked. Then, after he had sworn that it had full burn in, he asked me what burn in was (his credibility dropped to zero). Most of his technical expertise was in how they could deliver barrel quantities to me. Most commercial shops can't afford to "rub out" their furniture finishes as custom builders do, so burn in and rubbing characteristics that are important to me apparently are foreign to them. In 2011 I reviewed the General Finishes web site. They have a variety of water based varnish and polyurethane products in both their retail and professional product lines. Their only acrylic lacquer was in their pro line, and recommended sanding between coats (i.e. it does not burn in).

Someone arranged for me to get a sample gallon of Fuhr 345 to try. Eventually I learned that it was their Waterborne Varnish, not a lacquer, which excuses the lack of burn-in. The web site brags about it's ease of use and extreme durability. As noted above, I gave away most of the $60 gallon of finish, dumped the rest, and have refinished the test table, since the durability on my kitchen table was terrible. Fuhr 375 is a water based lacquer, but it requires sanding between coats, so apparently does not have burn in.

Another friend tried one of the Sherwin Williams water base finishes - I am not sure which one, but it was in response to my enthusiasm about Target coatings, and his reluctance to use mail order. Their results were poor, and when they went back to Sherwin Williams, the excuse was that they had not adjusted properly to the specific temperature and humidity in their spray booth (hard to adjust the humidity in the driveway).

Good luck! Your comments and feedback are appreciated.

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