Can I spray clear coat on wood?

Spraying clear coat on wood is a common finishing technique used by woodworkers, furniture makers, and DIYers. A clear coat provides a protective layer over stained or unfinished wood while allowing the beauty of the grain and color to show through. There are several factors to consider when deciding whether to spray a clear coat versus brushing it on. In general, spraying clear coat is faster and provides a more uniform, professional-looking finish compared to brushing. However, it requires some specialized tools and a bit of practice to master the technique.

What is a Clear Coat?

A clear coat is a transparent, protective finish that is applied over stained or bare wood. The purpose of a clear coat is to protect the wood from moisture, scratches, fading from UV exposure, and other potential damage. It also provides an attractive, smooth sheen.

Clear coats are available in various sheens ranging from matte to high gloss. They typically consist of varnish, polyurethane, lacquer or shellac. Here is a brief overview of each type:

Varnish:

Varnish provides a durable, flexible finish that resists moisture, scratches and alcohol. Traditional varnishes use an oil-resin blend while more modern water-based varnishes are lower in VOCs. Varnish dries slower than other clear coats.

Polyurethane:

Polyurethane is highly durable, protective and resistant to scratches, chemicals and heat. Oil-based polyurethane yellows over time while water-based options stay crystal clear. Polyurethane dries faster than varnish.

Lacquer:

Lacquer dries extremely fast to a very hard, durable finish. It provides good moisture resistance but can be prone to scratches and solvent damage. Lacquer sprays on easily for smooth results.

Shellac:

Shellac dries fast with good moisture resistance. It brings out a warm wood tone. However, shellac is not as durable or scratch resistant as other clear coats so requires more frequent recoating. It’s often used as a sealer before applying a different topcoat.

So in summary, clear coats enhance the look of wood while protecting it from wear and tear. Different resins have varying characteristics that make them suitable to the specific project needs.

Advantages of Spraying Clear Coat

There are several benefits to spraying a clear coat finish versus brushing:

Faster Application

Spraying clear coat goes on faster than brushing and requires less coats to achieve full coverage. With a spray gun, large surfaces can be coated evenly in a single pass. Brushing takes more time and often leaves noticeable brush strokes.

Smoother Finish

A sprayed clear coat provides an exceptionally smooth, professional looking finish. The fine spray mist levels smoothly without leaving any applicator marks. Brushing often leaves subtle brush strokes even with high quality brushes.

More Even Coverage

A spray gun coats all areas evenly, including hard to reach spots like edges and crevices. Brushing can sometimes lead to uneven coverage with drips or thin spots in difficult areas. Spraying ensures all wood surfaces get covered uniformly.

Higher Build

Spraying deposits more finish per coat, allowing you to achieve the desired film thickness faster. Brushing often requires applying many thin coats to build to the same level.

Less Drips and Runs

Applied properly, spraying lays down a smooth layer without drips forming on vertical surfaces or runs on horizontal areas. Brushing can lead to drips if too much finish is applied.

Minimal Brush Marks

A sprayed finish has no visible applicator marks compared to subtle but noticeable brush strokes. This leads to a flawless, professional look.

So for woodworking projects where a perfectly smooth, fast-drying film finish is desired, spraying has a clear advantage over brushing on clear coat.

Disadvantages of Spraying Clear Coat

While spraying clear coat has many benefits, there are some potential drawbacks as well:

Overspray

Spraying generates a fine mist of clear coat droplets. This overspray can drift onto surfaces where finish is not desired. Tarps and drop cloths are essential to protect floors and other areas from stray overspray.

Increased Equipment Costs

Spraying equipment like a compressor, hoses and a spray gun represent an added up-front investment. Brushing just requires high quality brushes.

Steeper Learning Curve

Achieving a flawless sprayed finish takes practice and experience. There are techniques to master include proper spray gun handling, distance and motion. Brushing has a more intuitive, straightforward learning curve.

Higher Risk of Contamination

Dust or bugs can get into the finish when spraying outdoors. Brushing in a controlled shop environment has lower contamination risks.

Hazardous Fumes

Spraying clear coats generates more overspray and fumes so requires adequate shop ventilation and protective equipment. Brushing produces less vapor hazards.

Lengthy Prep and Cleanup

Between masking surfaces, mixing finish and cleaning a spray gun, spraying involves more time-consuming prep and cleanup steps versus simply brushing.

While spraying clear coat has a steeper learning curve and higher investment costs, the end results are often worth it for many finishers. Proper spraying technique can minimize drawbacks like overspray.

Best Clear Coats for Spraying

Certain clear coat types lend themselves better to spraying application. Here are some top options:

Lacquer

Lacquer remains a very popular choice for sprayed clear coat finishes. It dries extremely fast, flows and levels nicely when sprayed, and requires no sanding between coats. Nitrocellulose lacquer sprays excellently.

Water-Based Polyurethane

Water-based polyurethanes apply easily with a spray gun. They level nicely and are low odor. Water-based poly dries slower than lacquer but faster than oil-based.

Pre-Catalyzed Lacquer

Pre-cat lacquers offer the fast drying and convenience of lacquer combined with the durability of varnish or polyurethane. Pre-cat flows and sprays on easily with full cure in under a week.

Conversion Varnish

Conversion varnish cures through a chemical reaction versus solvent evaporation. It provides extremely durable, chemical resistant protection ideal for restaurant tables and bar tops.

Shellac

Shellac is commonly spray applied as a seal coat when using a different topcoat finish. It dries very quickly and sands easily between coats.

These are excellent options, but most clear coats can be effectively sprayed with proper technique and thinning as needed. Oil-based polyurethane requires the most thinning for spray application.

How to Spray Clear Coat

Here is an overview of the key steps for successfully spray finishing clear coat on wood:

Prepare the Wood Surface

Ensure the wood surface is clean, dry and sanded up to at least 220 grit. Tack rag the wood just before spraying to remove any remaining dust. For previously stained wood, apply the clear coat within the finish manufacturer’s recommended window.

Select a Spray Gun & Compressor

Choose an HVLP spray gun designed for applying clear coat finishes. Match it with an adequate air compressor and hoses. Consult finish manufacturer specs to determine optimal spray gun tip size and air pressure.

Set Up a Spray Area

Cover surfaces surrounding the project with tarps, paper or plastic sheeting. Position projects in a spray booth or well ventilated area to direct overspray away from you. Wear an OSHA approved respirator.

Thin the Clear Coat (Optional)

Thinning is often unnecessary, but some products spray better diluted anywhere from 10-30% with the manufacturer’s compatible solvent. Always check the tech sheet.

Strain & Prepare the Clear Coat

Pour the clear coat through a paint strainer to catch any dried bits or skin that could clog the spray nozzle. Mix or stir thoroughly before pouring into the spray gun cup.

Adjust Air Pressure

Refer to finish instructions to set the ideal air pressure at the compressor and reduce it using the gun regulator. Lower pressure (8-10 PSI) works for thinner viscosity finishes like lacquer. Heavier finishes require more atomization pressure.

Apply the Clear Coat

Hold the spray gun perpendicular to the surface, 6-8 inches away. Move at a steady pace, overlapping passes by 50%. Apply 2-3 medium wet coats until reaching the recommended film thickness, allowing proper drying time between coats.

Allow to Fully Cure

Give the clear coat several days to a week to fully cure before use. Cure times vary by product. Test hardness before use. Apply another coat if the film can be dented by a fingernail.

With some practice using proper spray technique, you can achieve beautiful, professional-looking clear coat finishes on your woodworking projects.

Tips for Spraying Clear Coat

Follow these tips to get the best possible results when spray finishing with clear coat:

– Start with properly prepared wood

Sand wood to 220 grit before spraying clear coat for optimal adhesion. Any surface defects will only get magnified under the clear coat.

– Use high quality spray equipment

Invest in a top-rated spray gun suited for clear coats to get the best atomization and finish quality. An HVLP spray gun is ideal.

– Spray light, even coats

Applying the finish too wet leads to drips and runs. Mist on 2-3 medium-wet coats for optimal flow and drying.

– Maintain consistent spray motion

Move the spray gun at the same speed during the entire pass to ensure uniform thickness and prevent thin or thick spots.

– Overlap passes 50%

Overlap each spray pass halfway to efficiently build up the film thickness while preventing drips, thin areas or heavy lines.

– Spray perpendicular to the surface

Holding the spray gun at a consistent distance, perpendicular to the project avoids uneven coverage and dark lines on vertical surfaces.

– Allow proper dry time between coats

Rushing recoats before the solvent fully flashes off can cause blushing, haziness or other film defects.

– Wear an approved respirator

Use at minimum an N95 rated respirator mask or fresh air system to avoid inhaling solvent vapors when spraying finishes.

– Spray in a clean, dust-free area

Overspray droplets attract contaminants like dust. Spray in a spray booth if possible or an area protected from wind or dirt.

Following these best practices will help you spray clear coats like a professional to achieve flawless, protective finishes.

Clear Coat Spraying Problems and Solutions

When spraying clear coat, you may encounter some common problems. Here are some troubleshooting tips:

Problem	Potential Causes	Solutions
Drips and Runs	Applying finish too heavily, improper spray gun angle, spraying too close to surface	Apply lighter coats, hold spray gun perpendicular and farther from surface
Blushing or Hazing	Recoating too soon before prior coat has flashed off, cold temperatures or high humidity	Increase dry time between coats, spray in warmer area with less humidity
Orange Peel Texture	Finish drying too fast, gun tipped too far, spraying from too far away	Slow dry time by adding retarder solvent, keep spray gun perpendicular and closer to surface
Uneven Gloss	Inconsistent spray motion speed, spraying too far away	Maintain steady spray pace throughout pass, keep spray gun closer to workpiece
Overspray Dust	Spraying in non-clean area, not monitoring overspray	Cover surrounding areas, spray in clean space away from wind currents

Troubleshooting spray technique and making small adjustments to the product, environment or application process can remedy most common clear coat spraying issues.

Clear Coat Alternatives

While spraying provides the smoothest, most professional clear coat finishes, brushing is a viable option in many cases. Here are the pros and cons of clear coat application methods:

Spraying Clear Coat

Pros:

• Faster application
• Smoother, uniform finish
• Excellent for large surfaces
• Higher film build

Cons:

• Overspray requires masking off areas
• Higher equipment costs
• Steeper learning curve
• More prep and cleanup time

Brushing Clear Coat

Pros:

• Lower equipment investment
• Minimal overspray issues
• Easier for smaller projects
• Intuitive process with short learning curve

Cons:

• Slower application
• Brush strokes often visible
• Difficult getting even coverage on intricate pieces
• Potential for drips and runs

Wiping Clear Coat

Wiping varnish or polyurethane allows for a hand-rubbed look. Thinned clear coat is applied then wiped off with a rag before drying. This takes some finesse but provides a low luster finish that accentuates wood grain.

Oil Finishes

Oils like tung, linseed or Danish oil provide some protection while retaining a natural look. Oils are easy to apply by hand but require more frequent reapplication than film finishes.

So in many cases, brushing or wiping clear coat is a practical, effective alternative to spraying. Consider your specific project needs when deciding on the best application method.

Safety Tips for Spraying Clear Coat

While extremely useful, spraying clear coats involves some safety hazards. Follow these precautions:

• Work in a well-ventilated area and wear an OSHA approved respirator mask.
• Avoid ignition sources as spray fumes are flammable.
• Wear gloves and eye protection when spraying.
• Protect skin and eyes from exposure to clear coats as they can cause irritation.
• Clean spray equipment thoroughly after use to avoid fire risk.
• Follow all manufacturer safety warnings and instructions.
• Dispose of used rags properly as they can spontaneously combust when soaked with oil-based finishes.

With proper safety measures in place, spraying clear coat can be accomplished safely by hobbyists and professionals alike. Proper ventilation and protective equipment are critical.

Conclusion

Spraying clear coat allows you to efficiently apply a protective, attractive finish to accentuate wood grain. While requiring some investment in tools and learning, spraying provides flawless results superior to brushing. Lacquer, polyurethane and varnish all can be sprayed effectively. With practice using proper spray techniques and safety precautions, anyone can successfully spray clear coats. The results are well worth the effort for critical wood projects.