Producing a quality paint job is a multi-step procedure that demands proper choices at every stage. An important step for every pro-fessional painter is the selection of quality tools and equipment. That’s because the quality of your tools affects both the appearance of the finished paint job and its performance properties, ranging from scrub resistance to mildew resistance.

Poor quality equipment can contribute to a poor paint job. Quality tools, on the other hand, not only help deliver a better-looking,
longer-lasting paint job, but also save application time. This is important because the cost of your time on a job far outweighs the cost of materials. To get the greatest benefit from your investment
in time, effort and quality paint, make sure you apply the paint with quality tools.

In general, the type of project and the coating you use will determine the appropriate tools and correct application method. There are five basic categories of application tools: brushes, rollers, paint
pads, paint mitts and sprayers.

BRUSHES                                                     back to top

There are two general types of paint brushes – those made with natural-hair bristles and those made with synthetic bristles (generally nylon or polyester).

Quality natural bristle brushes are often preferred for use with oil-based or alkyd paints particularly for enamel or finish work. They are not recommended for use with water-based (latex) paints because natural bristles are hollow and can absorb up to 40% of their weight in water, causing them to become limp and difficult to use.

Use only synthetic bristle brushes when applying any type of water-based coating. They hold their shape and maintain proper stiffness regardless of the amount of water to which they are exposed. Be aware, however, that some brushes are available with synthetic bristles that are hollow and designed to act like natural bristles.

Many synthetic brushes also work well with oil-based and alkyd paints, although it is always wise to check the brush manufacturer’s usage instructions. When applying a coating made with strong solvents such as lacquer thinner, use only brushes recommended for these types of coatings.

Regardless of whether you plan to use a natural or synthetic bristle brush, it is always wise to use a high quality brush for nearly all types of work. Quality brushes apply paint in a thicker, smoother film, which provides maximum hiding and sheen uniformity. Conversely, lower-quality brushes often leave ridges in the paint where dirt can collect and mildew can grow. Paint with brushmarks in it can fail earlier in the thin spots.

Bristles

When choosing a paint brush, pay attention to the bristles. In a quality brush, the bristles should:

• Have flagged (split) ends to provide a finer, more even finish.
  
• Have a definite flex at their tips and spring back into shape.
  
• Be shorter on the outside and longer in the center, creating a tapered appearance. This type of chiseled brush helps you apply the paint smoothly and evenly, and gives you more control over where the paint is applied.
  
• Measure at least 1 1/2 times as long as the width of the brush. For example, the bristles on a quality 2" wide brush will be at
  least 3" long.

In addition, there should be no gaps in the bristles. When the bristles are pulled, no more than a few should come loose. If bristles pull out easily, the brush is probably poorly constructed.

Handle

A quality brush should also feel well balanced and comfortable in your hand. And the handle should feel neither too slippery nor too rough. Look for a handle of solid wood or synthetic rubber, but not hard, hollow plastic.

Many quality brushes have a handle of unfinished hardwood, such as beech or maple. This type handle will help you maintain a grip, whereas a painted or plastic handle will tend to become slippery in sweaty hands.

Plastic handles are also a poor mounting surface for the ferrule, which is the metal band that holds the bristles together. A top quality brush will have a rust-resistant metal ferrule that is attached with pins or brads, rather than by crimping.

Size and Shape                                                back to top

It is also important to match the size and shape of the brush to the paint job. Most jobs, both interior and exterior, will require several brushes of varying widths and shapes.

In general, a 4" wide flat brush with tightly packed bristles and a thickness of 3¼4" to 1" is the best all-purpose brush for most large exterior surfaces. Brushes between 3" and 4" wide are best for interior walls and ceilings.

A 2" brush with tapered edges is best for cutting in corners. Brushes between 1" and 21/2" wide work well on window frames, molding and woodwork. Angled sash brushes between 1" and 21/2" wide are excellent for precise painting of window frames and trim.

Application Tips

Using a paint brush properly is part art, part science. Here are some time-tested tips that will help you master brush application:

• Before dipping a brush into paint, dampen the brush slightly
  by wetting it with the liquid used in the particular paint (water
  for latex paints, paint thinner or mineral spirits for oil-based or alkyd paints). Squeeze, shake or blot all excess liquid from the brush so that just enough is left on the brush that it is damp.
  This is called priming the brush. It allows the paint to remain
  on the surface of the bristles and makes cleanup easier.
  
• When applying paint, dip only one-third to one-half the
  length of the bristles into the paint container.
  
• When first starting the job, repeatedly dip the bristles into
  the paint and work the paint into the brush by pressing the bristles against the inside wall of the container.
  
• When painting, tap the brush against the inside of the can
  to take off excess paint. Do not wipe paint off the bristles
  using the rim of the container.
  
• Do not overload the brush with paint. Dealing with the
  resulting drips and runs can take more time than you save
  by loading up with too much paint.
  
• Hold the brush lightly resting the thumb and fingers on
  the ferrule. Then apply paint at an angle about 30° from
  the surface.
  
• Use long, light, vertical strokes on walls. Vertical strokes
  are less tiring than horizontal strokes.
  
• Paint from the top down and work in manageable sections,
  four to six feet wide.
  
• Follow the grain when painting wood items such as doors.

Brushing Techniques

In general, when using a brush, use sufficient pressure to bend the tips of the bristles slightly. Also, whenever possible, use the wide side of the brush, and not the edge. Using the edge of the brush may cause bristles to bunch together permanently.

Feathering: Avoid lap marks by brushing toward the unpainted area and then back into the just-painted area. This is known as brushing wet to dry and produces a smooth uniform appearance. Finish off the leading edge of the brush stroke by gradually lifting the brush from
the surface. This is called feathering or tipping off.

Laying off: Another technique, known as laying off, refers to the process of going over a painted section with quick strokes in one direction to help cover any missed spots, to help hide brush marks
and to blend in laps. This technique works better with oil-based
paints because of their greater open time compared to latex paints.

Cutting in: When cutting in corners, apply paint about a half-inch wide by moving the brush away from the opposing surface. Then go back, moving the paint toward the opposing surface to fill in and make a clean edge. For interior work that requires both cutting in and roller application, do the cutting in along with the roller work to maintain a wet edge between the two areas.

Beading: If you’re not using a paint shield, use a beading technique
to cut in inside corners and ceiling/wall intersections when two different colors are involved. To create a bead, press the brush flat against the surface. This causes a thin line or bead of paint to form
at the tips of the bristles. Then draw the bead of paint against the edge of the wall being painted.

Note: While some extra brushing and working may improve the appearance of oil-based or alkyd paints, avoid excessive re-brushing when using water-based or latex paints, especially semigloss or gloss finishes. Just a few strokes per brushload with
latex paints will achieve a thick paint film with good hiding and flow.

While it may be possible to brush a latex flat paint out thinly and achieve good economy and appearance, other longer term properties will suffer. These include scrub and wear resistance on interior applications, and mildew resistance, crack resistance and general durability on exterior applications.

Cleanup

After a paint job is done, clean natural bristle brushes used with oil-based or alkyd products only with paint thinner. Shake excess thinner out of the brush after the last rinsing. Then dry the brush with paper towels to remove as much thinner as possible. Dispose of the paper towels properly, taking flammability into account.

Cleanup of synthetic bristle brushes depends on the paint used:

• If latex paint was used, clean the brush with warm water and detergent. Rinse thoroughly with plain water.
  
• If oil-based or alkyd paint was used, clean the brush with
  paint thinner, mineral spirits or VM&P naphtha. Repeat until the brush is free of paint, then clean with warm water and detergent;
  shake out excess. Remember that strong solvents such as
  lacquer thinner may damage a synthetic brush.

A protective wrapper normally comes with a quality brush and helps
to keep the bristles properly shaped and clean. It also prevents the bristles from spreading apart or breaking. After cleaning, hang brushes to dry and then return them to their protective wrapper or stiff paper. Lay brushes flat or preferably hang them for storage.

ROLLERS                                                     back to top

Rollers come in a wide range of widths. Standard roller widths are
7 1/2" and 9". The 9" size is suitable for most interior wall and ceiling jobs. Wider rollers (14" - 18") are available for efficient work over
large areas.

There are also many special purpose rollers in different sizes and shapes for use with trim, corners and pipes, as well as self-feeding rollers that have a continuous supply of pressure-fed paint or manual-fill types for very large paint jobs.

Rollers were patented in the early 1940s. And because they are faster and easier to use than brushes, they have become especially popular for painting interior walls and ceilings. About three times more paint can be transferred to the surface with a roller than a brush in the same amount of time.

However, there are drawbacks with rollers:

• They use more paint (more paint is wasted on cleaning
  or disposal with a roller than with a brush).
  
• They apply a thinner paint film.
  
• They can be difficult or impossible to use in small
  narrow spaces.

On the whole, though, rollers are quite suitable for large, flat interior surfaces, as well as rough exterior surfaces such as stucco and concrete. When applying two coats of paint, some painters will often apply the primer or first coat of paint by brush, and the second coat by roller.

A quality roller cover, or sleeve, is essential to ensure the best results. As with brushes, use synthetic covers when applying latex paints. Latex roller covers are usually made of polyester. Use covers with natural fibers (most often, lamb’s wool or mohair) for oil-based paints.

When using oil-based paints, check the type of roller cover to deter-mine whether the roller material can stand up to the paint. If it is not impervious to strong solvents, a roller cover core could be softened significantly during the paint job.

Roller Nap or Pile

A roller’s cover material or fabric is called the nap or pile. Roller covers come with varying nap lengths. In general, smoother surfaces require
a shorter nap; rougher surfaces require a longer nap. Also, the higher the gloss level of the paint, the shorter the nap.

Nap lengths are usually described as short, medium or long. Short
naps (1¼8" to 1¼4") are best for smooth plaster, wood or metal surfaces. Medium lengths (3¼8" to 1¼2") are recommended for semi-rough surfaces such as light-textured stucco, poured concrete and rough wood. Long naps (more than 1¼2") are best for concrete block, brick and rough stucco.

Quality Construction

As with brushes, there are several visual and “hands-on” inspections that can help you identify a quality roller:

• Make sure the roller cover has no obvious seams. Seams can cause streaks in the applied paint.
  
• A roller cover must hold its shape. Squeeze the roller to get an idea of how resilient it is. This will also let you know whether it has a consistency throughout or whether it has lumpy irregularities.
  
• The roller should be balanced and have a comfortable feel.
  
• The handle and frame should be a heavy gauge to ensure
  strength and durability. Economy handles and frames will
  bend easily.
  
• Roller frames come in a variety of styles. U-shaped frames are generally more sturdy.
  
• When choosing frames, be sure to select those that are sealed
  on the ends to help keep the paint on the roller.
  
• A quality roller cage holds its shape and transfers pressure
  evenly across the roller cover. Cages with more tines are
  more robust than versions with only a few tines.

Application Techniques

To obtain a quality paint job with a roller, it’s important that you apply the paint in a steady, labor-saving manner. Here are some procedures for applying paint with a roller:

Do not overfill a roller tray; about 1¼3 full is sufficient. A plastic or metal grid or screen placed in the roller tray will help ensure that the roller loads evenly with paint. Use a grid that is the same width as
your roller. Some painters also like to use a removable roller screen with one- and five-gallon pails.

Give a new roller cover a “rub-down” to remove loose nap. Some lint will come out of any new roller cover if it is rubbed. However, if it is excessive, roller cover lint will mar the appearance of the paint job. If this is the case, interrupt the job and replace the roller cover. Make the first rolling with a new roller cover on scrap wall board or paper to remove any entrapped air bubbles.

To minimize drying on the roller, moisten the roller cover before dipping it into the paint. Moisten the cover with water when using latex paints; with a little paint thinner when using oil-based paints. Squeeze out any excess liquid before beginning to paint, or use one
of the spinners that are commercially available. Then, blot the roller cover on paper towels or newsprint.

When using a roller, initially apply the paint in the form of a W, N
or M using an upward motion with even pressure to reduce the chance of dripping or spattering. Do not lift the roller from the surface, but continue to spread the paint by making a cross roll in the horizontal direction to fill in the areas between the initial strokes.

Roller strokes should be straight, and not dragged to the left or right. Finish with light strokes, all in the vertical direction slowly pulling the roller off the surface to get a feathering-in effect.

Roller Application Tips

• Roll fast enough to be productive, but not so fast that
  spattering occurs. Remember quality paints are less likely
  to have problems with spattering.
  
• Keep the roller adequately filled with paint. When it begins
  to make a tearing sound or “snap,” it needs more paint.
  
• Some pressure is appropriate, but watch for heavier lines
  of paint that may form at the end of the roller.
  
• Be sure that adjacent surfaces are protected from
  spattering with masking tape, paper, drop cloths or
  tarpaulins.
  
• As with brushing, always paint from the wet edge into
  the dry. This helps to minimize lap marks.
  
• Roll as close as possible to the edge of the ceiling to
  avoid seeing a pattern difference at the cut-in.
  
• If you re-use the same roller cover for different colors,
  start with the lightest color, then work in gradually darker
  colors, thoroughly washing the cover between colors.

Many painters eliminate the time and effort involved with cleaning roller covers by simply discarding the cover at the end of a job. (It always seems that a new cover gives the best finish.) Even if this the case, it is still important to use a quality roller cover.

PAINT PADS                                                back to top

Paint pads have one distinct advantage over brushes or rollers: they allow you to get to hard-to-reach spaces, such as corners and behind radiators, where neither brushes nor rollers will fit. Although larger pads can hold about twice as much paint as a 4" brush, some
of the smaller ones do not hold as much paint as brushes or rollers, and are not as versatile.

Most paint pads are made of a plastic foam, and are often cut in blocks or cut to appear like a paint brush. The pads come in different textures, depending on the desired effect, and are replaceable when worn. Some professional painters like pads for interior use when cutting in at the ceiling line.

A common type of paint pad is made of a piece of nylon fabric attached to a foam pad which attaches to a plastic plate with a handle. The pad can be removed from the plate so that it can be reused.

The pile of the nylon pad is similar to a roller cover and is about 3¼16". Lamb’s wool pads are ideal for applying exterior stains because they hold a lot of stain, are relatively dripless, and can be used on rough and textured surfaces.

Holders vary in size and can accommodate pads from 1" square to about 4" x 9". Large paint pads may come with a spring-loaded handle to help hold the pad flat. Some models have wheels that act as guides when painting against an adjoining wall, trim or ceiling.

Paint Pad Application Techniques

Load a paint pad by dipping it into a regular roller tray or a tray specially designed for pads. Float the pad in the paint or stain, being sure to wet only the fabric pad, not the foam or solid support.

Remove excess paint with a light wiping action of both the forward
and rear edges on a grid if there is one or on the ridges of the tray.

Applying paint with a paint pad is very different from painting with a brush or roller. Apply the paint with long, straight strokes, all in the same direction. Do not pull the pad back over the paint. Watch for lap marks which are more likely to occur since paint edges are difficult to feather with this tool.

When painting a flat wall with a pad, make an “X” over an area
of about 4-foot square. Fill in the square with horizontal strokes,
followed by light vertical downward strokes.

When painting a large area, start at an upper corner and work down
in a stripe. Keep the stripe manageable, about 2 - 2 1/2 feet wide. Repeat this technique with the next stripe, being sure to work into
the previous area to prevent drying and lap marks.

PAINT MITTS                                              back to top

Mitts are constructed of lamb’s wool or synthetic material that has been reversed. They are usually supplied with a plastic glove to wear inside the mitt to protect against penetration of the paint. Always use a protective glove, even if one is not supplied.

After dipping the paint mitt into the container of paint, wipe the mitt along the surface being painted. It is important to apply a sufficiently thick coat of paint when using a paint mitt. This comes with practice, so it is necessary to watch how much paint is used as the painting job progresses.

Unless you use a paint mitt frequently, it’s likely you’ll discard the mitt after each job. However, cleanup of a paint mitt is simply a matter of scraping off as much paint as possible.

Then place the mitt on the glove-protected hand, and squeeze and rub the mitt in solvent or warm soapy water if the paint was alkyd or latex, respectively. When the cleaning solution runs clear, wipe the mitt nearly dry with paper towels and then hang it to dry completely.

SPRAY PAINTING                                         back to top

There are four major types of spray painting: conventional, airless, air-assisted airless and high volume low pressure (HVLP), all of which use a controlled and highly engineered
mechanical delivery system. (Electrostatic methods can also be
used with all of these systems.)

One of the earliest commercial uses of conventional spray painting, which uses compressed air, was back in 1893 at the Chicago World’s Fair. Airless spraying came on the scene during the 1960s, and by the 1970s, had become a rising star as more and more painting contractors adopted the new technology. Conventional spraying took a second evolutionary path in the 1980s when high volume low pressure (HVLP) spray painting systems debuted.

Applications

The main reason contractors have used paint sprayers for more than
a century is their application speed and subsequent potential for reducing labor costs. You can cover large areas quickly by spray painting. In fact, it has been estimated that spraying can be as much as four times faster than brushing and twice as fast as rolling.

Spray painting is versatile and can be used to paint objects of varying geometry and of varying materials such as wood, masonry, brick and metal. In addition, because the dry film does not show brush marks or roller stipple, spray painting provides a very uniform appearance, an important advantage, especially for interior work.

On the other hand, a very smooth and uniform surface can be difficult to touch up well, particularly with satin or eggshell finishes. As a result, some builders insist that sprayed paint in new construction be back-rolled so that the job can be touched up.

Conventional Spraying                                  back to top

The design of the spray gun’s nozzle controls the spray pattern of the droplets and also directs the paint toward the surface. Atomization takes place either in the spray gun or immediately outside the spray
tip depending on the design.

Internal and External Mix

If atomization takes place inside the spray gun, it is called an internal mix. Internal mix guns offer the advantage of requiring less air pressure and less air volume. They also feature less overspray and apply a thicker coat of paint. Overspray, also called bounceback, refers to paint that misses its target.

If atomization takes place outside the gun, it is called an external mix. External mix guns are popular because they provide better control of the spray pattern and there is less wear on the gun.

With external mixing, a finer spray pattern can be obtained and there is the added advantage that it can be used with a siphon cup. Siphon model spray guns are usually external mix.

In a conventional spraying system, an air hose brings air through the handle of the gun to a valve that controls the amount of air released. Another valve at the back of the gun can change the shape of the spray pattern depending on the dimensions of the surface being sprayed. The paint is supplied through another hose from either a cup or a separate, larger container.

Cup Spray Systems

Cup sprayers are ideal for small jobs, especially if multiple colors
are used and changed often.

In a cup spray system, you must attach a cup of paint to the spray gun. The cups in this system usually hold one to two quarts of paint, and use either a siphon or a gravity feed setup to deliver the paint to the gun.

The siphon feed system works along the lines of a spray bottle or perfume mister. A drop in pressure at the top of the siphon tube is created when air is expelled from the gun. The lower pressure allows paint to be drawn up the tube where it is atomized at the spray cap.

Siphon cups divert some air to the siphoning mechanism to equalize the pressure in the cup. Consequently, somewhat higher air pressure may be required to get correct atomization. Siphon cups are not that popular with contractors because they often restrict access to spaces.

Gravity feed systems offer a way to control spray pattern without the complexity of the siphon. In this system, gravity simply forces the paint out of the cup into the gun, but the gun must be held in an upright position which some contractors may find awkward. Gravity and siphon feed paint sprayers are both well-suited for touchup and other jobs that require only a small amount of paint.

While gravity feed cups are capable of handling average viscosity coatings, they seem to have found a special niche in the application
of thick coatings and mastics. For example, in the automotive refinish market, gravity feed cups are used almost universally to spray paints and coatings, especially heavier ones such as primer surfacers.

Pressure Feed Systems

Larger jobs usually require conventional spraying systems that feed
the paint from containers ranging in size from 2 to 55 gallons, or larger.
In this case, the system will usually incorporate a pressure feed system in which compressed air pushes the paint from the container through the fluid hose to the gun. Pneumatic pumps can also be used for this purpose.

In a pressure feed system, the proportion of air to paint is determined by the viscosity or thickness of the paint, the pressure applied to the paint, and the volume of the air used to atomize the paint.

Paint Dilution

Conventional spraying equipment can apply many types of paint, from relatively thin lacquers to heavier coatings. As a result, painters appreciate the versatility of conventional spraying as well as its control and the quality look it delivers.

However, they also note that conventional spraying can be tricky to use because it sometimes requires adjusting the viscosity (thickness) of the paint. This is typically done by dilution with an appropriate liquid.

An important concern is the effect of dilution on the application properties and performance of the paint. For example, paint coverage, as measured by dry paint film thickness, will be reduced
for a given wet film thickness because dilution will lower the volume solids of the paint.

Dilution may also interfere with the balance of paint properties. This is because paint manufacturers optimize their formulations using a precise amount of pigment, binder, liquid and additives.

Additives, in particular, are designed to function optimally when present at a certain proportion in the paint. Too much dilution could throw this proportion out of balance.

Today, paint manufacturers often do not include dilution on their spraying application instructions, or list only a nominal amount such
as ½ pint of liquid per gallon of paint.

Safety

The fine mist formed by use of conventional spraying can be a serious issue because it enshrouds the painter in a fog of paint. The need for personal protective equipment, therefore, is very important.

Whenever spray painting, always review the Material Safety Data Sheet (MSDS) to select proper personal protection equipment such
as an approved respirator, safety goggles and gloves.

The fine mist also increases the chance for overspray. That’s why conventional spray systems generally have a low paint transfer efficiency, often as low as 30% - 40%. Transfer efficiency indicates the amount of paint sprayed that actually goes onto the surface
being painted, compared to the total amount used.

A low transfer efficiency not only means an economic loss to the contractor, but also increases the need to mask off and cover adjacent surfaces. In addition, overspray can be grounds for
insurance claims should it get into the air and settle on cars or buildings.

Conventional Spraying Techniques

Spray painting is a complex subject, and every contractor who wants to use this technique should follow the manufacturers’ recommendations for the proper use of their equipment. A few general guidelines are given here.

The most common mistake made with a conventional spray system and other types of spraying is arcing the gun while spraying. Arcing results when the wrist is kept rigid while the arm is moved. This creates an uneven coating that is heavy in the middle and light on
the ends. (Fig.1)

To prevent arcing, simply bend your wrist in order to keep the spray gun at right angles to the surface, and at a distance of
about 6" to 12" from the surface. (Fig.2) Holding the gun closer deposits more paint on the surface (which may result in unevenness and sagging) and produces a narrow spray pattern. Holding it farther from the surface results in a thin coat and a wider spray pattern.

Also, start your stroke before you pull the trigger, and continue it after releasing the trigger. If you don’t, there will be heavy spots of paint where you start and stop. Reverse your stroke direction and apply the return stroke in the same manner.

Moving the gun at a constant speed results in even coverage. The correct spraying speed allows for a full wet coat of paint without runs or sags. Overlap the edges of each spray stroke about 50% to get a uniform coating without streaks or thin spots.

Some painters find it helpful to frame a rectangular area with four spray strokes, then fill in the area. Others prefer to spray a grid or matrix of several perpendicular lines, then fill in the whole area with horizontal or vertical spray strokes.

Airless Spraying                                           back to top

1. Paints do not typically require any adjustments in
   their viscosity because the pressure is so high.
   
2. It has a high transfer efficiency because overspray
   is minimized.
   
3. It is considered by many to be the fastest method
   of applying paint.

The pressure at the nozzle of an airless sprayer is very high, typically 1500 psi or higher. The line pressure or pressure of the paint going to the spray gun can be 1800 to 2000 psi.

Tips can run from about .007" to .080", with fan widths from 2" to 3" up to 14" to 18". Tip sizes for painting walls and ceilings with conventional paints generally run .017" to .021", with a 10" to 12" fan.

The size and shape of the orifice in the spray nozzle controls the application of paint with an airless spray gun. Forcing the paint through this small hole creates the atomization effect.

Because the orifice is so small, it can become clogged if the paint contains grit, bits of dried paint, etc. As a result, many airless units and other types of spray units come equipped with strainers. Paint contractors often refer to these strainers as “rock catchers.”

An airless spray gun looks like a conventional spray gun except there
is only one hose connected to it … the paint supply hose. There is no air supply hose.

Pumps

The pump that supplies the paint to the spray gun can be mounted in different locations depending on the job. For example, the pump and paint container can be set on a dolly so that they can be easily moved around a job site. The pump can also be mounted on a five gallon pail of paint or on a drum with a siphon tube.

Electric pumps are typically used with airless spraying. They start at about 1¼2 horsepower (hp) and range up to 2 hp.

The horsepower has a direct correlation to the number of gallons per minute that the paint can be sprayed. However, there can be limitations on the electric power source available, particularly on residential jobs. Be sure to take this into account.

Pulsation of the spray can result in uneven application of the paint. If pulsating occurs, it is probably due to an inadequate pump size or a nozzle exceeding the pump capacity. This emphasizes the importance of balancing the system from pump to nozzle.

Applications

Airless spraying offers production speeds nearly double those of conventional spraying. It is more efficient due to reduced overspray.
It is also more portable, less cumbersome and easier to clean. Moreover, the potential for fire hazard when working with oil-based paints is reduced simply because far less spray mist is produced.

Airless spraying’s advantage for covering large areas is clear, but it may not be the best choice for smaller areas because of the pressure and the typical distances from the surface needed to get good application.

Safety

Most contractors use self-cleaning tips and quick-change tips, which should be tungsten carbide types. The gun should be rated for high pressure and must be equipped with a tip guard. OSHA requires the mandatory use of a tip guard because it can help prevent a major injury.

However, even with all these safety guards, it is still possible to accidentally inject yourself with the gun, which can cause serious bodily harm, or even be lethal.

Consequently, it is important that you periodically clean the tip guards because they can catch spray and allow a buildup to accumulate. Eventually, this buildup could be caught in the stream
and blown out at the surface.

Fibrous coatings such as block fillers are not suitable for airless spraying due to potential clogging and the possibility of blowing out hoses. There can also be a static buildup on airless hoses, so the unit is usually grounded.

Airless Spraying Techniques

Airless spraying techniques are similar to those of conventional spraying, with two exceptions:

1. Because of the higher pressure involved, maintain a distance of about 12" to 14" from the spray gun to the surface rather than the 6" to 12" for conventional spraying. If you hold the gun too close, paint buildup will cause sags and runs. If you hold it too
   far, you will get a thinner coat and more overspray.
   
2. Unlike conventional spraying which allows you to vary the paint flow, an airless system has only two settings: on and off. This makes it more difficult to control the paint flow. As a result, it is important to move the gun at a speed that is comfortable and provides proper coverage.

If you find yourself moving the gun too quickly in order to prevent excess paint buildup, lower the pressure or use a tip with a smaller orifice. If you find yourself moving it too slowly in order to get a good coating, raise the pressure or use a tip with a larger orifice.
Air-assisted Airless Spraying

Air-assisted spraying is a modification of airless spraying. In this type of equipment, an air hose is added to the airless spray gun so that air can be fed from a small air compressor. The spray gun has a special
tip to shape the fan pattern and a special air cap for atomization.

The pump pressure is lower than normal airless at about 1000 psi or less, and the air compressor is only about 20 psi. The result is a system that can cover large areas, but with better atomization than airless and less overspray.

HVLP SPRAYING                                          back to top

Some of the air pushes paint up the fluid tube into the nozzle. Another stream of air goes out through the nozzle and meets the paint, atomizing it at very low pressure, and forming a very fine mist that results in a minimal amount of overspray.

Some systems utilize single or multiple-stage turbines to move the air. Others use air compressors, which offer the advantages of quieter and cooler operation, better atomization and a smaller diameter hose.

When using an HVLP system utilizing turbines, be aware of the air temperature. Some turbines generate enough heat to start the paint drying as it is atomized. This can result in a dry spray which can cause a foggy cloud in a closed area, as well as a compromised paint job.

Applications

Transfer efficiency can be very high with HVLP, at least 60%, and approaching 90%. Because more paint reaches the surface, HVLP is very well suited for interior applications, when working in confined areas, or when painting trim, doors, frames, cabinets, shutters and other fine finish work.

HVLP is not typically used for large flat areas because the low air stream pressure results in a slower operation compared to airless spraying.

Paint Thinning

When initially introduced, HVLP systems were more suitable for thin coatings such as varnishes, but manufacturers have developed increasingly more powerful machines so that the range of paints has now expanded. However, HVLP still may not be able to handle heavy paints such as some latex or high solids coatings without thinning.

Unfortunately, thinning can result in a lower dry film thickness and reduced hiding that could require multiple coats, so production suffers. In addition, there is the concern that paint properties could be compromised. If dilution is necessary, no more than 10% dilution
should be used.

As an alternative to thinning, consider going to a higher horsepower
air compressor or to multistage turbines.

HVLP equipment manufacturers are continually adapting their systems to meet contractors’ needs. For example, most manufacturers now offer a variety of nozzles for special purposes or special applications. However, it is still possible to handle the full realm of coatings/applications with only one nozzle.

Manufacturers also offer options for handling high volume painting including the use of compressed air with an HVLP gun or an accessory kit to convert a pressure paint tank for use.

HVLP Spraying Techniques

HVLP spraying techniques are similar to those of conventional spraying such as holding the gun about 6" to 8" from the surface and over-lapping the sprayed areas by 50%.

The application speed of HVLP is as fast as or faster than con-ventional spraying. Compared to an airless system, however, HVLP is slower, which means you will have to work more slowly because the output will not be nearly as high as with an airless system.

To adjust application speed, change the nozzle size. Remember, the larger the nozzle, the faster the application. Also remember that an HVLP system may offer better control and a finer finish/atomization than an airless system.

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Conventional

Paint makers and spray gun manufacturers often supply charts to assist you in selecting the proper nozzle, tip and needle combination for conventional spraying. This combination, referred to as the nozzle combination or setup, is a matched set that determines the spray pattern.

This combination is important because if the tip is too big, the exit
rate of the paint will be too high and will not allow the air to atomize
it properly. If the tip is too small, not enough paint will come out of
the gun and application control and speed will be lost.

Airless

With an airless system, it is the combination of orifice size and fan width that determines the rate of paint flow. For example, if you
select a smaller orifice while maintaining the same fan width, the
result will be a thinner coat of paint applied over a large area. Correspondingly, if you maintain the same orifice size while decreasing the fan width, the result will be a thicker coat of paint applied over a smaller area.

It is important, therefore, that you know what tip you are using. Airless spray suppliers provide charts listing their tips along with the types of paints for which they should be used. Identifying numbers usually appear on the tip.

HVLP

Determining the spray gun nozzle combination or setup for HVLP systems is similar to that of conventional spraying. However, the air pressures involved are much lower, so the air cap and fluid tip are even more important. It is best to adhere to the guidelines of the gun manufacturer and the paint manufacturer to ensure the best job.

Note: Some government regulatory bodies have mandated that HVLP spray guns be fitted with an air nozzle test gauge for VOC compliance. Make sure that you are knowledgeable about all local, state or federal regulations pertaining to painting and especially to spray painting.

As you can see, a large number of factors impact spray application techniques. As a professional painting contractor, it is imperative that you master all these factors through consultation with the equipment supplier, with the paint manufacturer and through your own personal experience. Only then will you obtain the best quality paint job, and boost your reputation and your repeat business.

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