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Both departments take their allotted completion times from a published labor time database, so 4.5 hours should pass just as quickly in both shops. But, as you well know, the 4.5 hours of work takes longer to complete in the paint shop.
The difference of course, is the dry times. You can hang a new fender just as quickly as your considerable skill and fancy power tools will allow. But no matter how fast you block sand or how rapidly you wave the spray gun, the paint still has to dry before work can proceed.
Speeding up the dry times is a sure road to more paint production. And heat is the key.
You can attach an air-replacement furnace and raise the temperature inside the spraybooth to make the work dry faster. A great idea and $15,000 well-spent, but most paint work is performed only on a single panel or two. So heating the entire vehicle to cure a hood and one fender may not be the best choice. The average collision repair still hovers between $1,500 and $2,000, and several sources suggest that 75 percent of paint work requires less than one pint of paint, covering a panel or two.
Based on these averages, a portable infrared heat light is just what the doctor ordered.
Whether they cost $200 or $5,000, portable heat lights help paint production by beating nature at its own game. Paint dry times vary according to temperature, humidity and air movement. Raising the temperature dries paint faster. It not only drives out the solvent, making the finish dry to the touch, but it promotes the chemical cross link between the catalyst and the paint resin. The faster those two components hook up, the sooner the work can be delivered. Several IR (infrared) vendors suggest that dry times can be reduced by 60 percent over ambient, unassisted dry times when portable heat is carefully applied. And having paint work dry in less than half the time it takes now is a money machine, folks.
How Infrared Energy Waves Work
All portable heat lights share some components. The heater unit typically has a heat source, a reflector and control switching. All this is mounted on a sturdy stand of some kind. The heat source can be a bulb, a tube or an emitter. We’ll use the terms interchangeably here, but each vendor would be happy to explain why his or her version of a heat generator is valuable.
All infrared energy is part of the same electromagnetic spectrum that continually surrounds us. X-rays and ultraviolet energy waves are below the visible light spectrum, and infrared and short-wave radio waves are above the visible spectrum. We can see neither. Harnessing the infrared energy in an emitter of some kind enables us to cook food, guide missiles and cure paint.
Just so we’re on the same page, let’s talk for a moment about the visible light spectrum. You’re all familiar with a color wheel (you better be if you match colors). There are only three primary colors: red, yellow and blue. By combining them in pairs, the three secondary colors appear: Red plus yellow makes orange. Yellow plus blue makes green. Blue plus red makes violet. Put these six colors on the edge of a circle, and you’ve made a color wheel.
Imagine taking a scissors and cutting into the circle between violet and red, and then bending the edges flat to make a straight line. That straight line is the visible color spectrum. The color violet is on the left edge of the line, followed by blue, green, yellow, orange and red at the right edge of the line. Voila, the visible light spectrum.
Off to the far left beyond the color violet are invisible ultra-violet energy waves. Off to the far right past the color red are the invisible infrared energy waves. They have a much stronger heating effect that any other type of radiated energy.
Infrared energy waves come in three types:
- Long wave.
- Medium wave.
- Short wave.
The distance they describe is from the crest of one tiny electromagnetic wave to the next.
Long-wave infrared isn’t very desirable for curing automotive paints because it tends to heat the top of the paint film rather than penetrate through the paint to the substrate. Typical uses of long-wave infrared include the heat bulb in your bathroom ceiling and the bulb in the glass rotisserie at the grocery store with whole cooked chickens turning around inside. In both cases, the long-wave’s tendency to heat the surface (of you or the chicken) works fine.
Medium-wave infrared will penetrate through the paint film and heat the substrate. This is exactly the action we’re looking for. By warming the paint from the bottom up, the solvents are pushed out into the air. If you heat the top surface first, the solvents are trapped inside the paint film and will burst out causing little craters (called solvent popping).
Short-wave infrared also heats the substrate, not the surface, but penetrates faster than medium-wave. Short wave can heat so quickly that it’s possible to sizzle the fresh paint. Some short-wave units have a ramp-up setting that feeds the energy onto the surface gradually. Medium-wave units don’t need a ramp-up restriction since they take a few minutes to reach full heat.
Some Like It Hot (But Not Too Hot)
How hot is too hot? Once again, I wish I hadn’t slept through physics class. Who knew physics would have anything to do with autobody! Turns out spray guns (partial vacuums), spraybooths (air volume and speed), air compressors (pressure drop) and heat lights are all directly related to physics.
At issue is the emmisivity of the substrate. For example, a steel substrate (like a body panel) will only get so hot if the surrounding air is cooler than the panel. So I can point an infrared heat light at the steel panel and leave for lunch. The panel will only get to about 135-140 degrees (if the shop air is cooler than that) and stay there Ñ the point of emmisivity. Plastic substrate has an emmisivity point of about 180-185 degrees. If I point the heat light at the plastic bumper and head out to lunch, bad things will happen. The plastic may become hard and brittle internally and deform externally. Many vendors recommend covering thin plastic parts with reflective foil tape if they can’t be removed.
So how do you control the temperature of the panels?
The most expensive infrared heaters have a remote-temperature sensor that turns the unit on and off to prevent over-heating the panels. Failing that, something as simple as an egg timer and a wooden dowel can help to prevent overheating.
Most heat lights should be placed somewhere between 20 inches and 36 inches away from the panel (exact recommendations are available from your vendor). Too close and the panel will get too hot, possibly causing solvent pop or hard polishing of the topcoat. Too far away and the panel won’t get warm enough, possibly causing uncured spots.
Zip tie a wooden dowel of the correct length (24 inches, 30 inches, etc.) to the heat light stand and roll the stand toward the car until the dowel touches to establish the right distance for your unit. By the time the dowel breaks off (hey, it’s a body shop), everyone will have a pretty good idea how far the light should be from the panel.
Buy a nice loud egg timer and set the cook time (15 minutes, 20 minutes, etc.). When the timer dings, the panel is cooked. Pull the light away and allow it to cool down. In general, keep the light back a little further and set the timer for a little longer; less damage is liable to occur.
The Role of Reflectors
Depending on which style bulb/tube/emitter your unit uses, it will have a matching reflector behind it. These apparently simple bent-metal shields play a big part in how well your light works. They’re carefully shaped and positioned to provide the exact reflection required for your infrared source.
Because the environment in the paint shop is often filled with drifting overspray, the reflectors get covered with dried paint and primer. And this will affect how well your light functions.
Keeping the reflectors clean and correctly positioned makes a big difference. Many shops stop using their infrared lights because they don’t cure like they once did. Dirty bulbs and reflectors are the most likely culprits.
Control switching may be as simple as a plug-in pigtail with no on/off switch or as sophisticated as being able to turn on only some bulbs to some specific temperature. Larger units offer the option of turning on the bulbs in banks or sections to accommodate smaller jobs.
Be sure that every paint technician understands how to get the most from your particular unit. Units aren’t the same from brand to brand. Distances, temperatures, switches, procedures and cool down vary significantly. And using the light incorrectly can cost more time in re-dos than the light saves in dry time.
All infrared heat lights are line-of-sight only. They work like the beam from a flashlight Ñ only the portion of the car directly under the beam will get hot. There’s very little creep from the hot substrate, and adjacent areas will not get hot and cure if the light doesn’t shine directly onto them. If you try to cover too large an area, the edges will remain soft.
Most autobody repairs will require moving the light at least once to properly cook and cure paint work. The bigger the light bank, the larger the area covered. The bigger the light bank, the more cumbersome the stand that holds it.
The “It’s Too Bulky” Excuse
In my experience, the most common excuse for not using an infrared heat lamp is the bulky stand. It’s hard to wedge between two cars, it’s hard to maneuver across the shop floor and it’s just plain big, man.
But it’s big for good reason. The expensive part is the fancy bulbs-tubes-emitters in the head. The bulky stand is bulky because it is wide enough and long enough to prevent the light from tipping over when you roll it across air hoses and drain grates on the shop floor. Being in the autobody repair business, you’ve heard an “expensive” noise before, like when two Mercedes crunch into one another. I’ve heard the expensive noise of a $5,000 infrared heater falling over on its face. Boy do those hot bulbs break into a lot of pieces!
The light stand in many shops is not only large and unwieldy, but it’s heavier because the techs added weight to the bottom. Whether it’s a wheel or wheel/tire on the bottom of the $200 light or it’s cinder blocks strapped to the legs of a bigger unit, keeping these babies upright is a good idea. Despite the fact that they’re hard to maneuver around, they’re the absolute best way to increase production in the paint shop. Use ’em!
The Lights Pay Off
Can your shop do all this great stuff with the $200 heat lights alone? No. Many inexpensive units are long wave, not medium wave, and no cheapo is a short-wave generator. But I still think the little lights are useful. Each metalman should have one to heat body filler, seam sealer and primers. (By the way, if you use infrared heat on any style of body filler, it will dry tack-free.) Painters need at least a $1,000 infrared light, and I can make a pretty good case for the most expensive light at many thousands of dollars. The hours you save in dry times pay for the lights quickly.
I don’t see nearly enough shops using big lights. My best chance of finding an infrared light in use every day is in a Northern U.S. dealership shop. Why there?
First off, it’s cold for a lot of the year. And painters don’t have much trouble dragging out the big light when the shop is cold in the morning. It feels good. (In fact, the health care industry also is a big infrared light user. They treat muscle disorders, among other ailments, by heating the substrate Ñ your bones Ñ and radiating heat up though your muscles.)
Secondly, the dealership environment tends to focus more on production benchmarks. Because they’re tracking their numbers by department, they know how much paint work should be completed based on how much body work got done. (It’s less, by the way.) One of the quickest ways to get paint production up is to force dry the paint. So the dealer bought some fancy infrared lights and insists that the painters use them. And once the painters get over their whining about how inconvenient the lights are, they notice their production go up.
So why don’t more shops use infrared heat? Using heat to speed paint production is much like wearing an air supply respirator to spray isocyanates. It’s too much trouble for the painter, who’s always going so fast that he doesn’t have time for that malarkey. But air-supply respirators (Fed. Std. TC19C) prevent the painter from inhaling any paint fumes. Yet painters can’t be bothered to tug and tote the other air hose around. So they don’t.
Heat will make paint dry faster, period. Yet painters don’t like lugging that big, ungainly light stand around. So they don’t.
Let There Be Light!
If you’re going to resurrect your existing infrared heat light, maintenance is the key to long-term happiness. You know how the downdraft booth doesn’t work very well when the ceiling filters are plugged? The infrared heater won’t work very well when the emitter and the reflector aren’t both clean and aligned.
Don’t let little things make life difficult. Most large lights are 220V powered, but many shops don’t have enough 220V outlets. If your shop is dragging a 50-foot 220V extension cord around, no wonder no one uses the light. Get an electrician to install another couple of 220V outlets. (By the way, 220V welders may require special plugs and receptacles. Make sure the infrared light has appropriate power and wiring. They may not be the same.)
Would your unit be easier to use with bigger casters or better casters? I’ve seen several lights with custom-fabricated outriggers and little pneumatic tires that roll over anything on the shop floor. Build, modify, add weight down low, clean and adjust until your light is easy to use. Use it and paint will dry faster, I promise.
If you’re in the market for new infrared lights, do a careful “pencil sell” on your payback times. Those enviable production figures the vendor quotes you are probably possible if your painters use the light all the time. But I see very few lights in Southern climates. Hey, it’s already hot, right? Regardless, the lights also work well in hot-weather shops. More heat makes solvents evaporate and resins cross-link faster, even if it’s already 90 degrees. In humid climates, the light will do a great job of drying moisture-laden panels before filler or primer.
As you can tell, I’m a heat light fan. Your health would be better if you wore an air-supplied mask. Your paint will dry faster if you apply heat.
Ask to see the light demonstrated in your own shop and keep track of the times it’s in use. Compare between competitive lights. In some cases, the absolute fastest units cost significantly more than the mid-priced units. Get started with something you can afford. Once you see the increase in paint production your shop can achieve by heating the paint, you’ll be buying more lights anyway.
Writer Mark Clark, owner of Professional PBE Systems in Waterloo, Iowa, is a well-known industry speaker and consultant. He’s been a contributing editor to BodyShop Business since 1988.
The Lights Aren’t On, But Somebody’s Home