How to Choose Finish Sprayers

If you've used only an aerosol can to apply spray-on finish, you may balk – even panic -- at the notion of power spraying tools. But with the right equipment and techniques, any DIYer can create beautiful finishes while saving time and effort.

Woodworkers, remodelers and painting contractors know that a project's finish is essential to its appearance and longevity. Whether you're producing handcrafted furniture, sprucing up interior or exterior walls or finishing cabinets, doors and trim, the key to terrific results is on the surface: a top-quality coating applied with care. A power sprayer can be the ideal tool for producing professional-looking results quickly and easily. To get you started, here is a basic overview of the array of spray equipment available and guidelines for its use.

Four categories
Power sprayers can be grouped according to their modes of delivery. Each type has characteristics suited for certain kinds of projects and materials. They also operate differently, so understanding the basics of each is vital to your satisfaction with the tool and the resulting finish:

1. Conventional (air) sprayers consist of an air compressor, a spray gun and a hose. They combine compressed air with light-bodied finishes (such as lacquer, polyurethane or auto-body paint) to produce a fine mist. These tools are best suited for small to medium-size projects in a production-shop setting. Because conventional sprayers produce the most overspray (a characteristic called low transfer efficiency), they are the most polluting and wasteful type of sprayer. In fact, some areas of the country restrict their use.

Any spray project – even applying latex-base materials -- calls for eye protection, good ventilation and respiratory safeguards, but air sprayers require the operator to don a twin-cartridge, half-mask respirator (NOT a dust mask!). Also a good idea: hearing protection, a hat, goggles with side protection, protective clothing and gloves.

2. High-volume, low-pressure (HVLP) sprayers combine the use of less pressure (10 psi or lower) and air to create the finest mist. They provide a softer delivery, so they produce the least bounce-back, overspray and waste. They are best suited for applying lighter materials, primarily clear finishes and wood stain or thinned oil-base paints. Manufacturers of these systems offer user-friendly models (usually turbine-driven) for DIY applications. A two-stage design (for smaller projects) starts at about $200 and has less air power than the three- and four-stage models, which cost $400 and up and offer faster delivery of material. Use an HVLP sprayer to produce a factory-smooth finish on detail work such as furniture, doors, cabinets and trim.

HVLP sprayers are fixed at one pressure setting. To fine-tune the spray, you must adjust the finish's thickness, measured by timing its flow through a viscosity cup (think of an hourglass). You may also change the needle size on the gun if needed.

3. Airless sprayers use very high pressure (1,500 to 3,000 psi) to force the finish through a tiny tip, breaking the material down to fine droplets and shooting them onto the surface. You can use an airless system to apply thin stains and clear coatings as well as thick materials such as latex paint by adjusting the pressure setting and changing the tip size.

Coating manufacturers prescribe tip sizes (stated in thousandths of an inch) for each product. In general, a smaller tip (.009 to .013) is used for thin finishes (sealers, stains, lacquer), whereas a larger size (.015 to .019) is needed for applying heavier-bodied finishes (latex paint).

Tips vary in the size of the orifice, in fan size and in spray pattern (elliptical or round). You can apply a vertical band of finish when sweeping the gun from side to side or a horizontal band to apply in upward and downward strokes.< br/>

Airless systems feature two types of pumps: piston and diaphragm. Piston models are more durable and are preferred for spraying thicker materials. Because airless sprayers deliver the most gallons per minute (gpm) of finish, they're best for covering large areas (for example, staining a fence or painting exterior siding). Use these tools with great caution: The high pressure can literally inject the finish into your skin, so aim carefully.

4. Hand-held power sprayers (sometimes called buzz guns) are the most affordable type; prices start at about $60. These tools can provide an introduction to spraying for DIYers and offer the benefits of simple operation and easy application, especially on rough surfaces and small projects. However, their output is much less than that of airless systems, so application is slower, making them impractical for large projects.

Portable, affordable power sprayers use a motor to siphon paint or stain and push it through a small tip to atomize the liquid.

Traits and tips
Just as the scale of your project and the finish being applied determine your choice of sprayer type, the equipment itself dictates some of the how-to aspects of power spraying. For example, two vital variables are the pace at which you move the gun and the distance you hold the tip from the surface.

Because an HVLP sprayer produces a softer spray, you need to hold its tip just 6 to 8 in. from the surface and perform an even but quick pass. The tip of an airless sprayer, on the other hand, should be about 12 in. from the surface being coated and move at a slower – but still even – pace. Conventional (air) sprayers can be positioned 6 to 12 in. from the surface, depending on the pressure setting and viscosity of the material.

For an even finish, you must aim the spray squarely at the surface. If the gun is tilted downward, for example, the coating would be thicker along the top of the spray pattern.

These are general guidelines; the manufacturer's instructions will specify the best practices for each model of sprayer. Just keep in mind that pace and space matter greatly. In all cases – regardless of the type of equipment or finish -- these recommendations apply:

  • Be sure the finish material is thoroughly blended and has no lumps or contaminants.
  • Work in a dust-free zone, and clean all dust from the surface you'll be spraying.
  • To avoid pauses in workflow (and paint flow), be prepared with a sufficient supply of finish and have everything set up before you begin. Protect all surrounding surfaces with plastic and masking tape.
  • Regardless of how skilled you become, always practice on a large piece of cardboard or heavy paper to fine-tune equipment settings, your stroke and the finish's workability before you start spraying the actual project.
  • When spraying outside, choose a day when there is no breeze. If you're working indoors, maintain adequate ventilation without direct air movement (no fans or wind blowing toward the spray zone).
  • Remember that humidity and temperature affect performance. Sprayed finishes dry quickly; in an arid environment, the finish will have even less time to level out and can clog the spray tip if you pause.
  • Hold the gun perpendicular to the surface. If you tilt the gun or sweep in an arc, the finish film will be uneven.
  • To avoid sags, drips or runs, engage the sprayer only while your hand is in motion, and release the trigger before you end the sweep. In other words, begin and end your hand movement outside of the application area.
  • Overlap the bands of finish by 30 percent to 50 percent. As a guide, center the spray fan on the leading edge of the previous band.
  • Always, always clean spray equipment immediately and thoroughly.

To ensure that the finish material is free of impurities or lumps, filter it through a screen as you pour it into the sprayer reservoir. This results in a smoother coating and prevents clogs from stopping the flow in the system.

Other factors
So you've determined the right sprayer for the project, but the coating is spitting or dripping onto the surface. Before you blame the tool, check the coating manufacturer's instructions to ensure you're using the correct tip size, recommends Rick Mueller, a trainer for Behr. "Paint chemistry varies between products, meaning not all satin latex paints (for example) would work with the same size spray tip," Mueller says.

Another alternative may be to adjust the viscosity of the finish. Read the label for instructions on thinning the material and on choosing tip sizes. You can get even more details and advice from the finish manufacturer's technical data sheet (TDS). If the retailer doesn't have a TDS, you can usually find one at the company's Web site.

A primary factor in how paint performs in spray applications is the quality of the coating (which typically relates to its price). The solids in higher-grade paints are more finely ground and therefore less apt to wreak havoc with spray equipment.

As with most new experiences, applying a spray finish will become less intimidating with hands-on practice. For more details about paint spray systems, click on the printable PDF article below. If you follow these guidelines and the advice provided by the manufacturers of the equipment and the coating, you'll have a great start toward a beautiful finish.

How to buy
Aside from budget considerations, your choice of a power sprayer largely depends on the scale of your project and the type of finish you want to apply. Also consider how often you'll use the equipment, keeping in mind that renting is a good way to try out different machines and learn what features matter most to you. For example, is the spray fan easy to control? How well can you maneuver the gun, hose, tank, etc.? How complicated is disassembly and cleanup?

When you shop, keep in mind that the gallons per minute (gpm) rating indicates the capacity of the pump and is a good clue about the size of projects it will handle. The specs will also show the maximum tip size supported: the larger the number (maximum of .019), the more power the system has for pushing finish through the gun. These factors will be especially important if you're a handyman or part-time painter who is likely to use the equipment often. To help in your decision-making, here's a brief comparison of the four types of sprayers.

Click here to view a PDF of this article.