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HOW TO


PAINT SPRAYING
SPRAYING PAINT is the quickest way to complete a painting job. Spraying louvered shutters and doors, wicker furniture, iron railings, fences, gates, and detailed molding, is a lot faster than painting with a brush. Spraying a uniform coat of paint without runs, sags, drips, or sputters, is very tricky. If the gun is not adjusted correctly, or if the paint has not been prepared correctly, the paint may spray on too thin or too thick. Paint mist is may blow onto unintended surfaces. Good spray techniques require a steady hand, proper overlapping of spray patterns, and an even distance to the surface.

If any of these elements are missing, spraying paint produces a surface that is either covered with drips and sags, or is not covered properly.

Learning how to do a professional looking spray job takes a lot of practice, but is no more difficult than learning how to use any other tool in your shop. The first time you pull the trigger, you won't feel much control. Within an hour, you will get the feel of working with the sprayer and may never want to pick up a brush again.

TYPES OF SPRAYERS
In addition to the aerosol-type canned spray paint found in home centers and hardware stores everywhere, there are three types of paint spraying machines: Propulsion, airless and HVLP sprayers.

Propulsion Sprayers.
This type of machine is an electrically driven sprayer that "flips" or "spits" out small
droplets of paint. A wheel providing centrifugal force or a moving piston pressurizes the paint and emits it through the small tip of a spray gun at the end of a long hose. Generally, the standard parts that come with your gun are appropriate for all types of finish, but different tips are available for handling latex and oil-based paints, and for producing different spray patterns. The rate of spray and pressure are adjustable.
The hand-held electric sprayers found in home centers are one type of propulsion sprayers. For the hand-held unit, paint is supplied via a small paint pot that is attached to the handle. The smaller-type sprayer is great for most projects, and will most likely be the only one ever needed. Larger, professional models are fed by a large bucket of paint. Larger sprayers are ideal for handling big jobs, such as painting siding, but because they require considerable skill to operate, are expensive and demand careful maintenance, they are primarily by professional painting crews. (Fig.1)

Conventional Spray Gun and Compressor

This type of sprayer emits a finer mist of paint that is driven by forced air shot through the paint. These units cover large surfaces with a smooth finish, but because they require the additional purchase of an air compressor, are too expensive for a single paint job. However, with the proper attachments, the air compressor can also be used for nail guns or auto repair applications. Conventional spray guns have proven their value during a century of use, but they have one serious drawback: They are only 20 to 30 percent efficient. What this means is that over half of the material you're spraying is wasted. Some of this overspray can settle back onto the finished surface, making it feel dusty or sandy. Recently, many localities have passed laws aimed at reducing the release of air-borne pollutants and have prohibited the use of spray guns for exterior painting. (Fig.2)

High Volume/Low Pressure (HVLP).

These sprayers can work with either compressed air or continuous air supplied by a turbine. The result is a low-pressure spray that creates very little overspray. HVLP guns are 65 to 90 percent efficient, which means that most of the material ends up on the wood. If you are just starting out and don't already have a large compressor, consider purchasing an small, inexpensive turbine. (Fig.3)

Aerosol Spray Cans.
"Spray paint," as it is often called, is quick and easy for small jobs. The cost per square foot is comparatively high, so carefully consider the size of the surface before deciding to use cans.

To mix the paint in a can, shake it vigorously. You will hear a rattle inside the container as you flip it back and forth. The rattle comes from a small steel ball that is the "paint paddle" mixing the finish. If you don't shake the container long enough, the paint will come out very thin; or the pressure in the can, the propellant, will fizzle out before all the finish in the can is utilized. Shake a can repeatedly during use to keep the paint fluid. To clear the paint tip, turn the can upside down and press the spray nozzle until no more paint comes from the container. If the spray nozzle becomes damaged, you can buy new nozzles very inexpensively at most paint stores. If the hole in the nozzle becomes clogged with paint, you may be able to open it with a pin. (Fig.4)
SPRAYING BASICS
Before you get started with application, there are several basics that you should know. First, the preparation of surfaces to be spray painted must be exactly the same as for any painting project. Remove all cracked and peeling paint. The surfaces must be free from dirt, grease and oil as well as being adequately dry. The paint you apply to a surface (sprayed, brushed, or rolled) is only as good as the surface to which the paint is bonded. Take the time and make the base perfect. Refer to How-To Booklet #28 Exterior Painting and #29 Interior Painting for preparation advice.

When spraying indoors, the area must be well-ventilated. Wear a respirator mask when spraying so you do not inhale the fine mist. It is also prudent to wear eye protection-paint is a terrible eye irritant in any form.

Cover everything that you don't want painted with masking tape, newspaper, or dropcloths. Do not underestimate the overspray even from cans-plenty of protection is necessary. On exterior projects, cover or remove all light fixtures, hardware, and other ornaments. Cover any vents, ducts, or plumbing fixtures. When you start spraying, the work goes fast and stopping in the middle of a surface can cause a noticeable sag or color difference. Be sure to have everything prepared before you begin.

Thinning Paint. Straight out of the can, most paint is too thick to be sprayed. It must be diluted with the appropriate thinner-meaning paint thinner for oilbased paint, and a special thinner made for waterbased paint. The proportions are roughly two parts paint to one part thinner, however, it's fine to go a little heavy with the paint. To gauge the thickness, or viscosity, the paint, you'll need to use a viscosimeter. This tool, available at most paint stores, is basically a funnel that's used to test the viscosity of paint.
A full viscosimeter of thinned oil- or water-based paint should run through the meter to mere drips in 30 to 40 seconds. (FIG 5)

Be sure the paint is free of debris and dirt. Strain it if necessary. (Fig. 6)

Overspray. The number one danger in exterior spraying projects is overspray from the spray gun. The paint can float in the air for amazing distances and settle on passing or parked cars, on neighbor's windows, porches, decks, roofs, and so on. Some communities even have laws against using spray equipment outdoors, so before you do any spraying, check out the codes. Spray paint outside only on a calm day, and never spray around a corner or up over a roof unless the spray is blocked with a covering such as a piece of cardboard or dropcloth. To spray inside corners, spray the adjoining surfaces first. The overspray will paint the corners. At outside corners, point the gun toward the house surface, not around the corner. Don't try to spray guttersthere's too much potential to ruin a roof with paint droplets.

SPRAY PAINTING PROCESS

The following illusts°a, cns snow a hand-held propulsion sprayer because this is the most typically used type. The technique of pattern and spray movement is the same for larger spray guns and for aerosol cans.

Good technique involves a steady wrist making quick and sure spray passes. The spray gun should be 12 inches from the surface. If you cut the distance from the tip to the surface in half, you are putting about four times as much paint on at that point. If you move back 24 inches, the paint is far too diffused. All this makes for uneven results. Be consistent with the tip distance. (Fig. 7)

The spray gun must be in motion as it starts across the surface to be painted. As you pull the trigger on some spray guns, the first projection will be air followed by paint. Keep the nozzle of the gun at a 90-degree angle to the surface. The trick is to feather the

paint onto the surface as you start spraying, and then to feather the paint off the surface as you complete the arc with your arm. Hold your wrist firmly so the spray gun always remains at right angles to the surface.
The heaviest paint concentration will be in the center of the spray pattern and the edges of the pattern will feather out. As you go back and forth across the surface, you will have to lap these feathered edges so the paint will be the same thickness throughout. Never swing the spray gun in a wild arc. What happens is that the center of the stroke on the surface will have too much paint while the ends of the stroke will have too little paint. Do not stop your hand or hold the trigger too long.

Move the spray gun steadily back and forth.
Go slightly past the edges of the surface, keeping the gun even and the same distance

from the surface. Feather the edges of every swath of paint about one third of the way into the previous pass to ensure an even coat. If the spray gun is attached to a paint feeder hose (as opposed to a paint cup attachment), form a loop in the hose and hold it with one hand in order to keep the nozzle of the gun at a right angle. Don't try to support the gun and hose with only one hand. (Fig. 8)

It's irnportant to clean your spray gun very thoroughly. If you allow any finish to harden in the gun, it may become unusable, and will be very difficult to clean again. Here are some simple steps to follow:
• Spray solvent through the gun at the end of each day, or anytime you won't be using the gun for several hours. This is especially true for water base finishes and varnishes, which are difficult to remove when cured. The best solvent for all finishes is lacquer thinner.
• Remove the air nozzle and valve stem at the end of each day. Thoroughly clean the nozzle or keep it stored in lacquer cleaner solvent.
• If you're using a cup with a spray gun, clean the cup and gasket thoroughly. Be sure to keep the air inlet hole clean and open at all times. If this hole gets clogged with finish, the spray gun will start to sputter.



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