It's tough to beat the smooth, even appearance of a sprayed finish. But outfitting your shop with a spray gun, compressor, or turbine system can be a considerable investment.
Fortunately, there's a simpler option. Many popular woodworking finishes are available in aerosol spray cans, making it possible to get excellent results without investing in dedicated spray equipment.
Spray cans are especially convenient for small and medium-size woodworking projects. There's almost no equipment setup, and when you're finished, there aren't brushes or a spray gun to clean.
The secret is to treat the aerosol can like a spray gun. A smooth, even finish depends on good surface preparation, consistent spray distance, steady movement, overlapping passes, and several thin coats.
Prepare the Wood Before Spraying
A sprayed finish won't hide poor surface preparation. In fact, a smooth finish can make scratches and other surface defects even more noticeable.
Whether you plane, scrape, or sand the project, the goal is the same: Start with a clean, smooth surface.
Once the surface preparation is complete, remove the sanding dust thoroughly. Vacuum the project and wipe down the surface as appropriate for the finish you're applying.
[IMAGE 2: Surface preparation before applying an aerosol finish. Use 5363066_snip_1548832012706.png.]
Woodsmith Tip: Take a few minutes to inspect the project under good lighting before applying any finish. Scratches and glue residue are much easier to correct now than after you've started building coats of finish.
Find a Safe Place to Spray
Before you start spraying, find an appropriate place to work.
Aerosol finishes create both overspray and vapors, so spraying in the middle of a woodworking shop isn't a good idea unless the space is properly equipped for spray finishing.
Spraying outdoors can be a practical solution when the product directions and weather conditions allow it. Choose a clean area that's protected from excessive wind and airborne dust.
Wherever you work, protect the surrounding area from overspray. Large sheets of kraft paper or another disposable covering make cleanup easier.
Safety Note: Always follow the manufacturer's directions for ventilation, personal protective equipment, and safe application. Keep aerosol finishes and their vapors away from flames, sparks, heaters, and other ignition sources.
Plan Your Spraying Sequence
Before picking up the can, spend a minute thinking about how you'll spray the project.
On a table, cabinet, or other project with both inside and outside surfaces, I like to work from the inside out.
Spray the interior and less-visible areas first. Once you're satisfied with those surfaces, move on to the more prominent exterior faces.
This keeps the finishing process organized and lets you concentrate on getting the best results where they'll be most noticeable.
Prepare the Spray Can
Shake the can thoroughly according to the directions on the label. The finish needs to be properly mixed before you start spraying.
It's also a good idea to make a few test passes over scrap wood or cardboard.
This gives you a chance to see the width and shape of the spray pattern and get a feel for how quickly you need to move. It's much better to dial in your technique on scrap than on the project.
Apply Several Thin Coats
One of the most important rules of spray-can finishing is simple: Several thin coats are better than one or two heavy coats.
A heavy application can puddle, sag, or run. Instead, keep the can moving continuously across the workpiece and allow several light applications to gradually build the finish.
Don't start spraying directly over the project. Begin the spray just beyond one edge, move smoothly across the surface, and continue spraying until you've passed the opposite edge.
This prevents the beginning and end of each pass from depositing a concentrated spot of finish on the project.
Woodsmith Tip: Keep It Moving. Never stop the spray can over the workpiece. Even slowing down too much can deposit extra finish and create a sag or run.
Think of each pass as one continuous movement: Start off the workpiece → move across at a steady speed → finish beyond the opposite edge.
Keep the Spray Can Parallel to the Surface
Spray distance has a major effect on the quality of the finish.
Follow the recommended spraying distance printed on the can. About 10" to 12" is common for many aerosol finishes, but the product directions should determine the actual distance.
More important than the exact measurement is keeping that distance consistent throughout the pass.
A common mistake is swinging your arm in an arc.
As the can swings, the nozzle moves closer to the middle of the workpiece and farther away near the edges. The result can be a heavier application in the center and lighter coverage toward the ends.
Instead, move your entire arm parallel to the workpiece, keeping the nozzle the same distance from the surface from one end of the pass to the other.
A steady speed and consistent distance go a long way toward producing an even coat.
Overlap Each Spray Pass
The next key to even coverage is overlapping your passes.
Rather than placing each new spray pattern directly beside the previous one, allow the new pass to cover part of the area you just sprayed.
For the first coat on bare wood, I typically overlap each pass by about half the width of the spray pattern.
This creates an even application without deliberately laying down a heavy coat.
The basic pattern is easy to remember: Spray → move over half a pattern → spray → repeat. Combined with steady movement and consistent nozzle distance, overlapping the passes produces much more uniform coverage.
Build the Finish with Multiple Coats
One of the advantages of spraying is that each coat is relatively thin. Depending on the finish, temperature, and humidity, that can allow additional coats to be applied fairly quickly.
Lacquer, for example, dries quickly and may allow several coats to be applied in a day. Aerosol polyurethane generally requires more time between applications.
Always follow the recoat time printed on the can rather than relying on a single schedule for every finish.
After building the first few coats, I like to give the finish additional time to dry. Then the surface can be lightly sanded as needed before applying the final coats.
For many projects, that's all it takes to create a smooth, attractive surface.
Woodsmith Tip: Build It Slowly. Don't try to make the project look finished with the first coat. A light coat that dries properly is better than a heavy coat that runs. Let the finish build gradually with each successive application.
Advantages of Spray-Can Wood Finishes
Aerosol finishes have a lot going for them.
There's almost no equipment setup, cleanup is minimal, and you don't have to invest in dedicated spray equipment.
They're especially useful for: - Small and medium-size woodworking projects - Projects with lots of corners and detailed surfaces - Turnings and other irregular shapes - Small furniture components - Projects where brushing would be awkward - Occasional spray finishing For these kinds of jobs, the convenience of reaching for a spray can is hard to beat.
Drawbacks of Aerosol Finishes
Convenience comes with a few tradeoffs.
The first is cost. Aerosol finishes can become expensive when you're covering a large project. Some of what leaves the nozzle becomes overspray, and you're also paying for the aerosol delivery system.
For a large cabinet, table, or other substantial project, dedicated spray equipment may make more sense if you spray finishes regularly.
You're also limited to the finishes, colors, and sheens that manufacturers package in aerosol form.
For smaller projects, however, the convenience can easily outweigh those disadvantages.
Use a Preval Sprayer for Custom Finishes
There's another option when the finish you want isn't available in an aerosol can. A Preval sprayer combines a replaceable aerosol-powered spray unit with a separate glass container.
Instead of buying a finish that's already packaged in a spray can, you add your own finish to the container.
That makes this type of sprayer useful when you need a particular finish or want to work with a custom mixture.
Some finishes may need to be thinned to spray properly through this type of system. Check both the sprayer instructions and the finish manufacturer's recommendations before adding thinner. Different finishes have different requirements, so there's no single thinning ratio that's appropriate for every product.
For occasional spraying, this type of setup provides a useful middle ground between a conventional aerosol can and a complete spray-finishing system.
How to Get a Smooth Spray-Can Finish
Good spray-can finishing comes down to controlling a few simple variables.
Start with a smooth, clean surface. Apply several thin coats rather than a few heavy ones. Begin and end each pass beyond the edges of the project, keep the nozzle a consistent distance from the surface, and move the can parallel to the workpiece.
Most importantly, overlap each pass and keep moving at a steady pace.
Once you've practiced the technique a few times, an aerosol can becomes more than just a convenient way to apply finish. It's a useful finishing tool capable of producing a smooth, even surface without the expense and setup of a complete spray system.
