The Science of Paint - BodyShop Business

The Science of Paint

Funky flakes and effect pigments aren’t new, but it wasn’t until OEMs determined they were lucrative that they showed up on production vehicles. Now we’ve got rainbow, holograph and even glass-chip effects.

Much like the snazzy clothing designers pave the way for fashion, hobbyists pave the way for special paint effects. Bear with me: The Italian designers who show their expensive, one-of-a-kind dresses on the runway in Paris each spring are style setters, and once their designs hit the streets, other clothing houses incorporate the new waistline or hem length into their upscale clothes, too. Then, after a year or two, the new styles make their way onto clothes at the big retail chains.

Why does it take so long? Because clothing manufacturers for stores such as Sears must deal in huge volume, they can’t take a chance that consumers won’t like the new hem length or colors — so they wait until a trend has been firmly established in better clothiers before they make hundreds of thousands. They’re also faced with mass producing their designs by machine. An Italian designer’s clothes sell for thousands of dollars, not just because they’re "art," but because they have hundreds of hours in hand labor sewing them together.

The process of getting a fancy new color effect into production on automobiles works the same way. Hobbyists or hot-rodders were adding special flakes to their colors years before OEM car manufacturers offered them on production cars. The manufacturers first made sure that people liked the effect — and then that they could produce it without the hundreds of labor hours the street rodder spent creating his.

It may have taken years for OEMs to jump on the special-effects paint bandwagon, but now that they’re on it and they know there’s a market for them, they have no intention of slowing it down.

A Fake Flake
Pigments are added to paint to provide hiding and to create a color. For example, blue pigments and red pigments added to paint resin will make a purple color. To make an even more interesting color, "effect pigments" are added to paint.

The original effect pigments were aluminum particles left over from another process, like roof coatings. And in the late 1930s, several manufacturers of expensive autos mixed these aluminum flakes with their solid colors to create a finish with an attractive sparkle and an interesting color effect.

But these early metallic finishes didn’t have much twinkle because the aluminum particles weren’t very big nor were they a uniform size. The flakes were actually dredges, or by-products, of some other process involving aluminum.

A Flake Is Born
In the 1950s, Alcoa developed an aluminum flake for use in automotive paints. These flakes were brighter, larger and more similar in size to each other than the previous offerings. And these flashy new metallic finishes were just the ticket for the aspiring consumer of the 1950s.

Stylists at Ditzler (now PPG) coined the term "poly-chromatic" to describe the color effect. And while some paint brands described their offering as "metallic," Ditzler called its "poly" for short. Although poly is a marketing term and not a scientific description, Ditzler was trying to describe a color that had "many facets."

In fact, a color with reflectants in it has three distinct facets: the face, which is how the color looks head on; the flop, which is how the color looks from the side; and the flash, which is the reflectant throwing the light off to your eye as you pass between the face and the flop. Matching these special effect colors was, and is, difficult because the reflectants look different depending how they’re aligned within the paint film.

Flake offerings at this time were mostly made by the same supplier, and no matter which paint brand they appeared in, they were smoother than earlier offerings and available in two or three different sizes.

Flamboyant Flakes
Street rodders are quick to adopt any new color effects and are undeterred by the labor and material costs involved. The ’60s are a good example of this. The ’60s saw very large, flamboyant flakes that required a higher-solids resin to carry them and many coats of clear to cover the larger flakes.

Since a fancy paint job was a labor of love for most street rodders, they relished the opportunity not only to spend hours sanding and polishing, but even bragged to their peers about how long their particular paint effect took to create. And any of you who shot those huge flakes over a colored ground coat can attest to the many problems. For example, some flakes were so large they created a static electricity problem as they were squeezed out the fluid tip of the spray gun.

When other gearheads saw a special paint effect they liked, they were also willing to bury money and labor in their pride and joy. The OEM car factory, on the other hand, had to keep an eye on the cost and production complexity of any paint finish. The really large ’60s flakes were a vinyl product rather than aluminum, and none of these made it to OEM color production because they were even harder to keep in suspension than aluminum flakes.

Mica on the Scene
In the 1970s, Chrysler was the first car maker to incorporate mica reflectants into its paint jobs. Mica had been around since the 1920s and, in fact, Henry Ford had an early patent on mica pigments.

Mica, which is a natural element mined like ore and cut into flakes, offers a more interesting effect than an aluminum flake. Aluminum flake is like a mirror, polished on two sides but dark on the edge. Mica is like a prism — some light is reflected and some is transmitted. And coating a mica flake with titanium powder yields a pigment that mimics pearlescence.

There are three sources of reflectants to create this pearl effect: Fish scales were added to nail polish in the 1920s to make her ladyship’s nails look cool, and street rodders in Southern California (where else!) tried adding fish scales to their auto finishes as well. One problem with fish scales was the durability. Once suspended within the paint film, the ultraviolet rays of the sun quickly destroyed them. Another source to create a pearlescent-looking finish is to add scrapings from the inside of sea shells. Also called nacre or mother-of-pearl, these reflectants were somewhat more lightfast than fish scales but were difficult to create in a uniform size. Lastly, there’s titanium-coated mica, which is relatively easy to produce in uniform size and is much more durable than either natural source of pearlescence.

As we’ve discussed, incorporating any special-effect pigment into an OEM finish is much different from painting a single street rod because the paint finish would appear on cars sold throughout the United States, if not the world, and the conditions vary from place to place. Two or three years in the Florida sunshine tended to eat any fancy finish rapidly, and a single winter in the Northwoods would crack a thick custom finish in minutes when the temperature dropped to umpteen below zero. In addition, the color effect had to be repeatable in different manufacturing plants — and, as we all know, this problem is better but still ongoing.

Improvements in clears played a huge part in making snazzy paint jobs available from OEMs. Once the solids level in clears went up sufficiently to support reflectants, the next step was to improve UV resistance. Suppliers got better at coating mica slivers so they would be more resistant to the sun, but the real advances were made when we could create a clear clearcoat that would withstand the sun for years without degrading. Remember also that clearcoating cars was always a hobbyist goal, but only recently could the OEM color stylists justify the cost to paint a vehicle a second (or third) time. What was their justification? Consumer demand. If enough people would buy cars painted with peanut butter, you’d see manufacturers changing their lines to apply it.

Three-Stage Pearls Take The Stage
While Chrysler’s cars in the ’70s had coated mica mixed in with the basecoat color, a more interesting effect is possible when the pearl pigments are applied over a solid base color in a translucent middle coat.

The first true three-stage pearl appeared on street rods in the late 1950s, but it was Audi that developed the first mass-produced true pearl finish. (The pearlescent effect is maximized when the base color is white because more light is reflected).

Typically, the first factory custom paint jobs always appear on more expensive vehicles. Remember the "Firemist" colors on 1970’s Cadillacs? They were the first to use big flakes in the color. Three-stage pearl finishes were also found on more expensive models in a manufacturer’s lineup. After all, who would have $800-$1,000 to spend over and above the cost of the car for a special paint job? Consumers who want something different on their already-expensive cars.

But what about trying to repair this "something different"? How have shop owners and technicians adapted to it? My real-world experience with three-stage pearls has been pretty good. Granted, my customers were apprehensive about their first one, but if they made themselves a test panel to duplicate the thickness of the middle coats to match OEM, the results have been positive. Recently, while talking with someone from a paint company, I suggested that this might be because the finish was very different from the regular base/clear paint job and, as a result, technicians at the factory were paying close attention when these cars were painted — resulting in a consistent color from car to car. While he thought this might contribute, he felt the main reason these custom finishes were repaired comparatively easily was that there was no evaluation point to compare the old finish with the repair. Since the pearl pigment reflected light in several shades, it was much easier to repair it invisibly. A solid color that doesn’t match is easy to spot by simply looking across the finish. A pearl finish, on the other hand, throws off so many different shades that there’s no one point to compare.

At the End of the Rainbow
If the Joe-average car factory is now offering a three-stage pearl finish, where’s the leading edge of effect pigments? The paint manufacturers all know that to answer this question, they need to look no further than the custom-finish market — the testbed for new color effects.

In fact, several new flakes are already available to you and your painters. One style is a type of cut vinyl flake made in very thin layers like the skin of an onion. These flakes can be smaller in size, but they offer more reflectance than larger previous-generation flakes. Several color effects are also possible, including a rainbow result where the exact same piece of flake may show a different color depending on the angle of the light.

These rainbow flakes can be mixed in with the base color, sprayed on over a base or even mixed in with a tinted clear over a different color base. And the best ideas are the ones winning trophies at the car shows.

Holy Holographs!
One of the most interesting effect pigments I’ve ever seen is the style that first appeared on a few of Ford’s Mustangs. These "Mystic" Mustangs sported "holographic" flakes made by a patented process with very expensive machinery. Briefly the process works something like this: The huge machine makes a perfectly flat (best reflector) aluminum particle that’s bonded to leaves of translucent material.

The Mystic Mustangs were painted with the very same flake that’s used in the ink on the new counterfeit-proof money. The flake was protected by armed guards when transported to Ford, and every gram was accounted for because, if stolen, detecting a counterfeit bill would be nearly impossible.

Other paint manufacturers now have similar flakes, but only BASF can match those original Mustangs. The other offerings are made by a similar process and are available in nine or 10 colors, none of which look like the ink on the new bills.

There are two ways to create this holographic effect. One style is a hiding finish, where the base color contains the flake and must only be cleared to be complete. A less expensive method is to create a cheaper flake by bonding layers together and then applying it in a three-stage system. The base color is applied first, then the special flake is suspended in clear and finally the whole is cleared. This method substitutes labor cost for flake cost.

Paint manufacturers try to give painters options by offering a chip chart or color selector, showing a few of the possible combinations. After all, not everyone has a good imagination, and some folks prefer to choose the effect right off a color card. Others, however, look at the card and envision what would happen if they combined several flakes and tinted clears.

How long before these holographic flakes make their way into other automobile production? Car manufacturers want to be sure there’s a market that will buy the special paint effect in sufficient numbers to pay back their investment in equipment and processes. But we may be getting closer. Although one paint company’s holographic flake sells by the ounce and is very expensive, it’s still sold more than $1 million worth since its introduction. Those are the kinds of numbers that will soon make some high-line car manufacturer want to re-create the type of effect originally seen on the Mustangs.

What’s Next?
In the works right now are colored aluminum flakes. In fact, General Motors already has an organically colored green flake in production.

There’s also ground glass, which has been around for decades but was round in shape. Many overhead street signs are already painted with glass reflectors in the paint (street signs are painted laying flat on the ground), but the problem with painting cars was that round orbs of glass didn’t want to stick to the vertical sides of the car. A new process, however, has been able to create a colored flat glass "flake." Likely used in either a two- or three-stage finish, it’s said to reflect lots of light and would be an easy switch for OEM paint lines. In the same vein, a specially coated man-made silica flake has the potential to produce a brilliant color effect with minimal light.

No matter which direction reflectants in automotive color go, one thing is for sure: Paint really has changed. Today’s paints offer many more options than yesterday’s, and paints of the future will, no doubt, offer even more options. Who knows, if you can combine these future colors and flakes creatively enough, your paint jobs may not only win awards, but they may also inspire the next cool paint job from the factory.

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.

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