A Place to Paint
We've all heard of cars that received a fantastic show-winning finish while being sprayed in a garage, barn, or even a driveway or carport. The fact is that quality painting requires a quality environment to work in-and safety recommends the use of a professional spray booth for all painting activities. True, few of us have the good fortune of a pro-quality paint booth for our one-off project ambitions, but nearly anyone can find access to a booth with a little legwork. Often a pro facility will be willing to rent booth time to hobbyists at a nominal fee. A pro facility will usually come with a professional-level air supply, the specific lighting needed, and most importantly, the proper ventilation system that ensures a safe paint project. The modern paint booth contains high powered fans that draw the air through filters, and downward, taking the unwanted overspray away from the vehicle being painted.
Air and Air Supply
A need that is a vital part of any paint project is, of course, a compressed air source to operate the spray equipment at the time the paint and primer materials are applied. Further, most autobody power tools are traditionally air powered, running the range from air sanders and body files, to reciprocating saws, grinders, and in some instances, even the buffers and polishers. The bottom line is that a paint project requires a reliable and ample supply of air. When it comes to compressors, it is typically the case that too much is never a problem, but falling short in terms of required air delivery at a critical point of the job can spell disaster.
Air compressors are most commonly rated in terms of volume by Standard Cubic Feet per Minute (SCFM), which is a measure of the volume of air delivered per minute of run time. Be aware that the volume delivered is greater at low pressure than at higher output pressures, so it's important to note the pressure (PSI) at which the volume (SCFM) specification is rated. For instance, a compressor may put out 11 SCFM at 40 psi, but at 125 psi, that output may be only 5-6 SCFM. Another consideration is the size of the storage tank which receives the compressed air. A larger tank will considerably cut down on the duty cycle of a properly-sized compressor, while providing a more stable air supply.
How much compressor is enough? At a minimum, this will depend upon the requirements of the tools being used, and fortunately most are also rated in SCFM for air consumption. As with the compressor output, it's important to note the pressure at which the tool's air consumption is rated. It also pays to figure a margin of about 50 percent over capacity when comparing the compressor output to the requirements of the tools. When it comes to compressors, the golden rule is that bigger is almost always better, and that goes for both capacity and storage tank size.
Presuming air of sufficient quantity is available, the next and equally important factor is air quality. Compressed air can often contain moisture that will condense into water at the tool or spray equipment, and water will certainly foul the paint. Oil contamination is also a possibility, often from worn or inadequately maintained compressors. The key here is to make sure the air compressor is in good mechanical condition, and the air delivery system is set up with a minimum of one water trap/separator. Another item that should be included in the air delivery system is a true pressure regulator. This will provide a stable and constant air pressure to the spray gun or equipment independent of the pressure fluctuations in the storage tank. A further regulator or choke is used at the spray equipment to set the air pressure at the tool.
Spray Equipment: Paint Guns
It used to be that just a few standard units dominated the field of autobody refinishing. These guns were predominantly conventional suction-feed types manufactured by DeVilbiss, Binks, and Sharpe. The landscape changed with the introduction of High Volume Low Pressure (HVLP) equipment more than a decade ago, initially introduced to cut waste and emissions from spray equipment in keeping with regulatory requirements. While the older conventional-style equipment is still capable of providing excellent results, the modern HVLP equipment has come to dominate the industry.
These modern guns have become highly refined and offer excellent atomization of the paint fluid, with restrained overspray and a more defined paint pattern, cutting substantially on the paint lost to the atmosphere, reducing paint material quantity requirements in the process. Most of this equipment is designed with a top-mounted paint supply reservoir cup, rather than the bottom-mounted cup typically used with traditional suction-feed spray equipment. This design also cut on waste by virtually eliminating the leftover paint in a suction-feed cup.
A skilled painter can achieve excellent results with a wide variety of quality spray equipment, and as a general rule, the more expensive spray gun models offer a finer finish quality. The professional-grade equipment is typically better serviced by the paint supply dealers that carry a particular line of spray guns, with accessories such as air caps and fluid nozzles with specific orifices to handle different materials such as paint or heavy primer. Generally, the pros will use dedicated paint guns for primer, paint, and sometimes even clearcoat. Another specialty gun that is worth considering is a small touch-up gun, which can be incredibly useful for tighter areas or small self-contained jobs such as the engine bay or jambs. A novice painter can do well with a single high-quality general purpose gun. When it comes to successfully applying paint, experience and familiarity with the specific spray equipment is nearly as important as the specific equipment itself.
No matter what the type of paint gun, it's virtually a requirement to have some sort of device mounted at the air inlet to regulate the airflow and pressure through the gun. These units can be a true regulator, or a simple adjustable choke-style restrictor, favored by many painters. The regulator or choke at the gun should work in conjunction with the main supply regulator, which is normally set at somewhat higher than the required pressure. A pressure gauge is usually, but not always, incorporated at the gun regulator or choke.
There are a variety of consumable supplies that should be on hand whenever a refinish job is contemplated. Some of these are mandatory, while others are added insurance to guard against problems and to achieve a professional result. The most basic of these supplies are sticks and strainers, used to stir and filter the liquid paint. These come as wooden paddles and disposable paper and gauze filters, which are often provided free of charge as a courtesy of the paint supplier. Another handy item for use while mixing the paint components is a graduated mixing cup. Usually these have multiple ratio scales corresponding to the common mixing ratios for the product being used. Similarly, measuring sticks are another alternative, this time with the ratio graduations being marked along the length of the mixing stick. Paint gun liners are another category of consumable supplies, providing a disposable lining for the paint gun cup, helping to ensure cleanliness and easing clean-up after the job is done.
Also fitting the category of a consumable supply are disposable moisture separators that are mounted right at the air inlet of the spray gun. Consider these a last line of defense against moisture droplets contaminating the paintwork. While on the subject of consumable supplies, don't neglect the air filtration on the paint booth itself. While the filters are designed to trap debris and dust, dirty filters can actually become a source of these airborne contaminants which can quickly damage an otherwise perfect paint job. Make sure the filters in the facility are clean, and replace them if necessary.
Personal Protection Equipment
An area of required equipment that's often overlooked, but which may be the most important of all, is safety and personal protection. While we've all seen old-timers spraying various products with just a dust mask, if anything at all, many of today's paint products can be highly hazardous to your health, whether inhaled or absorbed through your skin. Various materials have differing levels of hazard and required precautions. It's important to be aware of these requirements and take the recommended precautions.
The most common level of protection would include disposable gloves, lint-free paint coveralls (typically disposable), a cartridge-style respirator rated for the material being sprayed, and a full head covering sock. Especially nasty brews of paints may have requirements that exceed this level of protection, and may require full head-gear with a respiratory air supply. Precautions should be observed at all stages of paint handling, not simply while in the booth doing the actual spraying. This includes protection from contact and vapors during mixing.
Clearly, the health aspects here are the primary concern; however, there is also the consideration of minimizing the potential for contamination of the paintwork itself. Lint from street clothes, the oils from skin contact on the car's surface, or a stray hair or two can ruin the paint work in a hurry. Using the recommended protective gear will not only protect the paint applicator, but it will protect the paintwork at the same time.