The best painters in the best paint shops remind me of Boy Scouts. Is it because they can light their cigarettes by rubbing two sticks together? Or because they can make a sanding block out of a pinewood derby car? No, it’s because they exhibit that most famous Boy Scout trait: “Be prepared.”
In far too many shops, the painters can always make time to do the job again but can’t seem to find the time to get it right on the first try. Rather than scramble around redoing a poor result, the Boy Scout painters I know deliberately spend time making sure all the elements are in place to deliver a top-notch repair on the first (and only paid) try.
I contend that to duplicate their excellent results, your shop would have to devote attention to five areas: the compressed air, the spraybooth, the vehicle, the color and the spray gun.
Maintain That Air Compressor
While this is truly the heart of any paint shop, it seldom receives any attention until problems develop. A poorly maintained air compressor can blow oil by the piston rings, which appears as white droplets on the vehicle surface. The oil is actually riding along on a water droplet. Together, they can cause fisheyes and poor adhesion. A poorly maintained air compressor will struggle to get enough air if the intake filter is plugged. Compressors must take in large volumes of clean filtered air on each stroke of the pistons or turn of the rotary screw. Since the body shop atmosphere is often full of sanding dust, the cooling fins on the compressor head are typically covered with dirt, which prevents them from dissipating the heat properly. Dusty conditions quickly plug filters and cover cooling fins.
A regular service at set intervals (monthly in extremely busy paint shops or quarterly in most shops) will prevent many problems. Air compressor manufacturers typically call for non-automotive lubricating oils for the best results. However, many compressor manufacturers from my past interviews have said they’ll trade the exact oil type for more frequent oil changes, even if you use automotive motor oils. New oil keeps the pump spinning smoothly, and a new filter element will keep the unit breathing freely.
Most air compressor problems that plague the paint shop are moisture related. When the compressor pump takes in atmospheric air (14.7 pounds per square inch or PSI) and squeezes (compresses) it to 175 PSI, lots of heat is generated. The fins cast into the compressor pump, and the fins on the piping that carry the air from cylinder to cylinder and to the tank (receiver), are all designed to offer more surface area to the ambient air. More surface area equals more opportunity to cool the compressed air inside. For every 20 degrees F you drop the air temperature, one-half the moisture in the air condenses to liquid water, which is easily removed from the compressed air. Water vapor (hotter temperature), however, is difficult to remove from compressed air.
So that we’re clear on why moisture in the air line is a problem, here’s what happens to the paint finish. Moisture vapor that hasn’t been trapped out by the time it reaches the spray gun will likely condense on the cool surface of the vehicle, inside the paint film. These water blisters (worst case) or white hazing (more common) will surely cause a redo. The whole secret is to cool down the compressed air sufficiently so that almost all the moisture vapor turns liquid.
Hotter air holds more moisture. That’s why the humidity is uncomfortable in Houston in the summer and non-existent in Detroit in the cold winter. My Boy Scout painters cool their compressed air. Examples include keeping all the cooling fins free of dust and dirt buildup, plumbing the shop airlines with high-pressure copper or aluminum pipe (both dissipate heat quickly) and locating moisture traps far enough from the compressor head that the air cools off on the way to the trap. If your shop has a moisture trap screwed into the side of the air tank, it’s doing no good. The air is still hot (180 degree F) when it leaves the compressor head, and little heat is lost by the time it leaves the tank. A rule of thumb is to locate the first moisture trap at least 25 feet from the receiver, and more is better. The farther the compressed air travels down the pipe, the more heat is lost and the more water turns liquid.
The most common paint shop moisture trap is an “impact”-type trap. The air is smashed against a barrier inside the trap and all the liquid water falls to the bottom, ready to be drained away. Any moisture that’s still hot passes right through the trap and condenses farther down the line. Regular draining of these traps keeps the liquid water from being swept back into the air as the trap fills up. Refrigerated air dryers are a great way to cool the air and remove the water. Basically, they pass the hot air over refrigerated coils (like your air conditioner at home), immediately lowering the temperature, and almost all the water condenses. Once liquid, it’s easily trapped out with an impact trap (contained inside the unit.) Desiccant dryers will trap even moisture vapor that hasn’t condensed to liquid. However, the desiccant material must be replaced or dried out regularly; otherwise, the water will act just like those games in the penny arcade. The whole floor of the game is covered with coins; the next coin to land in front of the push bar will shove coins over the edge (or so it appears). When the desiccant is fully loaded, the next drop of water in the unit will shove a drop out into the air line.
The disposable screw-on filters for the spray gun are loaded with desiccant beads or leaves of paper or cotton wadding and trap moisture vapor perfectly. Until they’re full, the next drop of water in pushes one out. The problem is they give no signal when they’re full. It’s better to address your compressed air moisture problems on a larger scale. Keep the air moving around the compressor pump (don’t keep it in a tiny, hot closet,) keep the fins clean, don’t use plastic pipe (holds heat) and drain the traps regularly (every day in the winter, every hour in the summer).
Focus on Filters
Automotive spraybooths are big, fireproof boxes. Required by law or code in most cities, they hope to contain the flames if the flammable paint catches fire. They also provide the best opportunity to produce a clean, fault-free repaint.
While most paint shops spend more time maintaining their booth than their air compressors, more attention here will help finish quality, too. A crossdraft spraybooth has intake filters in one end and exhaust filters in the other. Air is pulled across the car by an exhaust fan typically moving 10,000 cubic feet per minute (CFM). Downdraft spraybooths have intake filters in the ceiling and exhaust filters in the floor, pulling the air top to bottom inside the booth at 10,000 to 12,000 CFM. In either case, an air replacement furnace can be attached to the spraybooth to “make up” for
the 10,000 to 12,000 CFM the fan
If you have an air-makeup unit, you also have another set of filters which filter the air before the furnace heats it. When any of the three sets of booth filters begin to plug, air movement and dirt content are affected. The gauge to measure filter condition is called a manometer, which measures the resistance from one side of the filter to the other. As the filter plugs, resistance increases. Many paint booths have no manometers fitted, and the painter must judge filter replacement intervals by opinion. My Boy Scout painters have a formula based on gallons of material sprayed or number of vehicles painted to accurately replace filter sets.
The filters replaced most often are the exhaust filters, correctly called arrestors. These plug quickly, as they’re designed to trap the wet paint overspray before it can be blown out into the atmosphere or onto the neighbor’s parked car. Arrestors are the least expensive filter set in a spraybooth, and many shops replace theirs weekly. Allowing the arrestors to remain in place too long will cause turbulent air movement inside the booth. Color and clearcoats can dry unevenly, dirt is kicked back into the airflow and onto the vehicle, and air quality within the booth can be even less healthy than usual.
Using the same air replacement furnace filters for too long will cause even the most expensive filters to plug even faster. The most expensive spraybooth filters are the intake filters – either the set mounted in the door of your crossdraft or the ceiling of your downdraft. In the case of a downdraft booth, these intake filters are actually what makes your booth function correctly. Called air-balancing filters, they’re such a sophisticated weave of paper and cloth that they’re designed not to let any air pass through them until the pressure is equal across the face of the filtered area, hence the balanced airflow. These are often expensive at $700 to $900 a set. Many paint shops try to make them last way too long, but this is a false economy, as my Boy Scout painters know.
If the ceiling filters become loaded and aren’t replaced, the dirt and imperfections in the paint work increase dramatically. Here’s a little math to make the case for more frequent replacement. The national average door rate is $40 per hour; every minute of a painter’s time is worth $0.67 ($40/60 minutes). If the painter, or the helper, must spend as little as 30 extra minutes cutting and buffing out dirt, each car will cost the shop $20.10 (30 x $0.67) in extra labor. Figure three cars a day through the dirty booth, so every day the shop spends an unnecessary $60. If the new filters were only $800 for the set, the shop could buy a new set every 14 days and be money ahead.
In addition to regular and careful filter replacement, the booth needs to be cleaned professionally at least once each year. The top of the booth and both the intake and exhaust stacking should be vacuumed clean by a professional furnace cleaning company. Panel seams, door seals and light fixtures should be examined, caulked, repaired or replaced on a regular schedule. In far too many paint shops, the last time anyone checked the door seals and stacking was when the booth was installed. Good painters know an ounce of prevention is worth a pound of cure.
Clean That Car
Good scouts know that at least one-third of the dirt in the paint work comes in on the car. Most paint shops solvent-wipe the vehicle to be painted at least once or twice, some as many as four separate times. However, they’re missing one of the easiest and most effective preparation steps they can employ: washing the car with soap and water, which removes water-soluble contaminants. Most importantly, shops should give the car a drenching water rinse. This flood of water cleans out the drip rails, cracks and crevices that solvent-wiping never reaches. For some shops, this may mean a change in procedure. If the car comes already masked from the metal shop, it’s hard to wash it next. Of all the tips in this article, rinsing the car with a water hose before painting
is probably the most dramatic improvement. Yet few shops do it.
Every painter tack-wipes the car before painting. My Boy Scout painters know that unfolding the tack rag and wadding it into a loose ball will do a much better job than unfolding it like a handkerchief. And yes, I understand it may take a minute ($0.67 of labor time) to pick the tack rag apart to its full size. But the loose ball’s ability to pick up dust is increased many times over, so it’s a minute well spent. When performing the final blowoff with a blow gun, make sure the booth fan is running. Also, try to point the blow gun toward the balled up tack rag as you work around and across the car, which keeps the dust from flying up and landing back on the vehicle.
One last word about masking technique: Good Scouts take the time to tape down all the loose edges of masking paper or plastic film. Anything that can flap when the compressed air from the spray gun passes by can cause dirt and dust to land in the fresh finish. Spending a few minutes carefully taping down all the edges and seams in the masking material will ensure the job only needs to be painted one time. After all, the shop will only get paid once to paint the car.
Have a Color Match Credo
This is what keeps Sears and Wal-Mart from opening a body shop: Locating and applying the color to match the thousands of color offerings and hundreds of different plant application techniques and doing it all quickly are too big an unknown for those retailers. They’ll leave that job to professionals like you. My best Boy Scout painters always start the color match process early. They’re never matching color in the booth; for them, the car is in the booth to be painted, not matched.
Most paint companies have spent hundreds of thousands of dollars on their color tools, so make sure your shop fully utilizes their offerings. Variant color decks, VIN-based color tracking, tintable sealers, spectrophotometers, color maps and good ol’ chip books are all designed to locate the best color match quickly. But as you know, finding the most likely color formula doesn’t guarantee an acceptable match. Many of the desired results (invisible repairs) are up to the painter. A color tool that’s underused is color match training classes provided by the paint manufacturers. While many painters (and managers) complain that they can’t be absent from work for the necessary two to four class days away at school, those training days can make life much easier for years to come.
My Boy Scout painters attended the color match training offered by their paint brand of choice. As a result, they don’t hesitate when the color isn’t an exact match. They’re willing and able to plot out the location of the car color and the mix on paper and, by examining the formula, determine which tint base will be needed (or eliminated) to achieve a blendable color match. Blendable is the key word. Those painters who think the customer is shortchanged unless they can butt-match the repair are spending needless hours in search of an unnecessary goal. The customer cares only that she can’t see the repair. A stepped-out blend is the fastest way to achieve that result.
Good Boy Scouts also believe in shooting test panels. Long before the car arrives in the paint booth, they’ve sprayed and cleared enough test panels to locate a formula and application technique to match the color. They also have a nice library of past test panels, each with the formula, additional tints, air pressures and reduction recorded on the back. Remember, painters get paid on refinish time. Finding a blendable match by employing past test panels saves time!
Spray Gun Fun
What Boy Scout wouldn’t like playing with an automotive spray gun? They have lots of knobs and levers, and a satisfying “hisssss” when the trigger is pulled and paint comes out of the nozzle. The best painters actually adjust their spray gun every time. Less talented painters never adjust their gun and try to overcome pattern and atomization shortfalls with technique. Here are a few tips to get the best results:
- Set the air pressure at the wall-mounted regulator (not the cheater valve on the gun) with air flowing through the gun. Even today, I meet painters who say they can set the correct atomization pressure by sound or feel. Baloney. With HVLP guns, there isn’t enough pressure to get the kick of the old siphon feed guns, nor is the difference between “hisssss” and “HISSSSS” accurate enough to set by sound. Good Scouts always use the diaphragm-type regulator to set pressure.
- Always test the spray pattern on a clean white piece of paper. Look for a uniform wet line with no gaps. Examine the droplet size within the wet oval. Adjust the trigger travel or PSI to achieve small enough droplets to quickly cover the surface. Too large and you’ll have an orange-peel effect; too small and paint will blow off target into the air.
- Spray at a consistent distance from the target and strive for a uniform overlap of each pass onto the next. The vehicle was painted at the factory by robots that stayed exactly the same distance from the panel on every pass. They also dropped an exact 50 percent of the next pass onto the previous one. Best color-and-effect match is achieved when the painter duplicates that uniform technique.
The Money Coat
All the great work the techs in
the metal shop did and all the surface prep the paint department did are invisible to the customer. All Mrs. Smith sees is the result of the final color and clear application. Boy Scouts know that a clean, glossy finish and an invisible color blend will cause Mrs. Smith to recommend their shop to her friends. Ensure this by always walking the customer out to her car and reselling the repair. When she agrees you’ve done a good job, ask her to recommend your shop. If you simply hand her the keys in the office and point to the car in the lot, she’ll never hear all the careful things you did to achieve the repair. If you don’t ask for her recommendation, she’s unlikely to offer one. Re-sell every job on delivery.
Trustworthy, loyal, helpful, friendly, courteous, kind, obedient, cheerful, thrifty, brave, clean and reverent, well… not all the painters I know qualify on all counts. But the ones who get the job right on the first try are…prepared. Spend time this week tuning up your compressor, booth, color retrieval techniques and spray gun adjustments. You’ll be glad you did.
Writer Mark Clark, owner of Professional PBE Systems in Waterloo, Iowa, is a well-known industry speaker and consultant. He’s celebrating his 20th year as a contributing editor for BodyShop Business.