The Perfect Match
Perhaps the most challenging task in the body shop is matching paint used for a repair job with the original paint from the factory. This is especially true with metallic and other specialty paints. When a vehicle is damaged, the owner expects their vehicle to look the same as it did before the accident.
Removing dents and fixing other collision-type damage, while time consuming in some cases, is not often a source of comebacks to the shop. Panel alignment and gap widths can be a headache, too, but nothing is more frustrating than not being able to achive a blendable paint match. Let’s face it, it’s a tough job that requires skill and experience.
THE SUN, ARTIFICIAL LIGHT AND COLOR
The paint that is applied to the repaired area of a car should look like the paint on the rest of the car. That’s a no brainer. But what do we mean when we say this? How do you really know that the repair paint is a blendable match to the original paint? While this task is subjective, the best method to verify that both are the same, or as close to the same as possible, is to look at the surfaces in sunlight. To understand this concept, let’s talk about the sun, light and color.
When you look at an object of a particular color (let’s say blue), the reason that you see that particular color is because all of the other colors have been absorbed by the object. In other words, if you look at a blue wall, it is blue because all the colors are absorbed except blue. If all light sources were the same, the light used to evaluate a repair paint job wouldn’t matter. All light sources, however, are not created equal.
The sun shows all the possible colors. The light from the sun, when passed through a prism, breaks down into all the basic colors: red, orange, yellow, green, blue, indigo and violet (Figure 1). Not all artificial light sources show all these colors. Fluorescent light has more violets and reds than other colors, while the incandescent light has more yellows, oranges and reds. The blue wall might not look as blue with these other sources (Figure 2). And since the vehicle being repaired will be seen the vast majority of time in sunlight, sunlight or an accepted substitute, should be used to compare colors.
Color-corrected light bulbs, used by photographers, most closely match the full spectrum of the sun. These bulbs can be purchased at a photography supply store. The Color Rendering Index, or CRI, is the index that is used to rate indoor lighting, such as color-corrected bulbs. A rating of 100 is equivalent to sunlight. The lights in your spray booth should have a rating in the range of 85 to 100.
Other important parameters are light temperature and brightness. Temperature is measured in degrees Kelvin. Sunlight is 6200 degrees Kelvin. The recommended light temperature range for booth spraying is 6000 to 7000 degrees Kelvin. The rating for brightness is the lumen. Most lamps are in the 1000-2000 range, with those approaching 2000 being the brightest.
Remember, the color of the vehicle does not change. What changes, under different light sources, is the amount of colored light that is absorbed and reflected. That is why using sunlight as the standard source of light will give you the truest version of 
that color.
SEEING COLOR
In addition to the light source having an effect on the color you see, your eyes can also be a variable. Did you know that roughly 1 in 8 men have some type of color blindness? In a male dominated industry, if you have a painter who has great technique, but has problems matching colors, the problem could be his eyes. This disease can be detected using Ishihara plates.
Color blindness cannot be corrected, but the problem can be solved by using a woman to verify color matches. That’s what the OEM guys do at the factory. The reason is simple. Women are rarely affected by color blindness (about 1 in 230). Also, women have a better memory for color. They are a natural, literally, for judging and evaluating color.
PAINT MATCHING TECHNIQUES
Paint looks different when it is wet compared to when it’s dry. Paint on a color chip or a stir stick looks different than what is in the can. The most accurate method of matching a solid or metallic color is to use a color test panel. This panel is a black and white coated sheet of cardboard or metal attached to a wooden handle. Tape the panel, then paint it using the same techniques that you use to paint a vehicle (gun adjustments, distance and speed). After the paint has fully cured and dried, compare it to the OEM finish. Adjust your mixture or tint, as required.
After you have formulated the correct mixture, you have to paint the repaired area. There are several problems that can occur. The most common are listed below:
(1) The color is over or under reduced
(2) Improper spray procedures (too close/too far or too fast/too slow)
(3) The color is improperly stirred or shaken
(4) Inaccurate mixing of the color formula
(5) Evaluating color under poor lighting
Techniques can always be corrected and refined. Remember, the closer you spray to the surface, the wetter the paint will appear. This also happens when you slow down your speed. This wetter look will make the paint look darker than if it were painted dryer (faster and/or farther away). Using these techniques are fine as long as that is the desired look. As a general rule, though, it’s better to paint dryer and apply a couple of coats rather than spraying one wet coat. You can always make a finish look darker by applying more paint, but you cannot remove darkness.
Proper mixing of paint is critical in achieving the correct color match. Be sure the paint is stirred and mixed thoroughly and that all pigments and metallics are in solution. This is especially true of metallic paint. The tiny metal particles in metallic paint must be homogenous (dispersed equally) in the paint (Figure 3). If you let your gun sit for as little as 15 minutes, the mixture is no longer homogenous and it will show on the surface of the car.
A few pointers about clear coat are in order, too. The applied thickness of the clear coat has a significant effect on the depth of a color. The depth of the color increases with the thickness of the clear coat. This is especially true with light metallic colors. To correct such a problem, talk with your paint manufacturer. Ask what the recommended thickness should be.
Remember this rule when blending the refinish paint into original paint. The original paint already has a layer of clear coat on it. As you blend into the original paint, reduce the clear coat thickness. If you don’t, the transition area will appear darker due to the thicker clear coat layer (original layer plus the sprayed layer).
TRI-COAT PAINTS
Tri-coat paints, such as pearl coats, are the hardest colors to match. These paints use a synthetic pearl luster pigment of mica particles covered with a thin layer of titanium dioxide. This layer provides a rainbow, or pearl effect to the paint. There are several points to remember when applying pearl coats.
1. Keep the paint agitated to evenly distribute the mica flakes
2. Spray test panels
3. Do not rush the paint job
4. Spray in a well-lit booth
5. Use an ultraviolet light to check the pearl effect
6. Check the paint from three angles; straight on and from both sides of the repair area
7. Match the basecoat before applying the pearl coat
