Painters must be able to match the color, cast, shade, metallic orientation and texture as they are refinishing the vehicle; otherwise the new work will be obvious.
To start the painting process, painters must first retrieve the OEM color code, convert it to their paint manufacturer's code and retrieve the formula. This task can become more difficult when, because of factory differences, there may be more than one shade or color variance within the OEM color. With a good variance deck and a color-corrected light, though, a painter can select the proper formula. Then it is off to the paint-mixing department to measure out the proper colors, using the color formula. If the formula is not poured accurately here, the color will be off. The painter must then reduce and catalyze the paint, choosing the proper combination for the current conditions, all of which could affect the final color.
Next, to check that the mixed color is a blendable match, a spray-out panel is made, using the exact gun and technique that will be used to spray the vehicle. Then, in sun-corrected light, the panel is compared to the vehicle's color to evaluate the color match. Once the painter is satisfied that the color is correct, the vehicle can be sprayed. During this step, if the painter's application technique is not precise or the blending technique used is incorrect, it could have an adverse affect on the outcome of the color.
Looking in detail at each step in color matching will help the paint technician achieve an undetectable repair every time.
Retrieving the OEM code
If finding the OEM code were as simple as looking on the door or trunk, the job would be simple. With computerized color retrieval systems, this task seems simple enough. I guess that would be the case if all vehicle manufacturers placed their color codes in the same location. In fact, it would even be great if the color code were placed in the same location on all of the products of a single manufacturer. Often, though, to find an unfamiliar vehicle's paint code, the painter's first challenge is to find the code on that particular make and model. This information could be found in a computerized estimating system, or in the paint manufacturer's code location directory. Even a Google search might be needed to find the paint code location.Once the vehicle's paint code is located, the technician must convert it into the paint manufacturer's code and then retrieve the formula. A nice feature recently introduced into some paint color retrieval systems is that when a vehicle's Vehicle Identification Number (VIN) is entered into the computer, the paint formula can be found using it alone. Once the paint code is converted, though, it still may not match.
Vehicles using the same code and color, but painted at different factories and with different batches of paint, could have slight differences (variances) within the same code. When paint suppliers become aware of these variances, they create a slightly different formula to compensate. Then, a variance deck is created that the painter can compare to the vehicle, so a sprayable match can be found.Mixing the formula
After a technician has chosen the correct color, a formula can be chosen and poured. The pouring process must be carried out precisely. If a formula measurement is even slightly overpoured or underpoured, it can cause the color to differ greatly from the variance. In turn, the mistake will cause the color that appears to be perfect for a blendable match to be un-blendable. It would be nice if a tint or toner that is poured either plus or minus 1 or 2 will still match, but each color has differing strengths. One may be considered "high strength," and even a slight amount of that color may vary the end color widely. On the other hand, if a less strong color is over- or un-derpoured, it may not make much difference at all.
Paint pouring systems mechanically dispense each color in a chosen formula with computer-controlled accuracy. The computer can often also calculate the exact amount of paint that will be needed for a par-ticular job. With the advantages of eliminating the possibility of inaccurate pouring, and avoiding extra expense by making only the precise amount of paint that is needed, a computerized paint pouring system can be a valuable addition to the paint matching process — and to the painter and the shop.
Reduction
The accuracy of the final color can also depend upon proper choice of reducer for the conditions, and on the choice of hardeners that will be added for the type of painting being done. It is an old painter saying that "anything that makes the paint go on wetter will darken the color, and anything that makes the paint go on drier will lighten the color." The statement holds true when choosing a reducer or hardener. Reducers that cause the paint to be applied or to stay wetter longer may cause the paint to darken. On the other hand, if the paint is applied too dry or not wet enough, the paint has a tendency to lighten slightly.Sprayout panel
Even with all the precautions a painter has already taken, there is but one way to tell if the paint will truly match, and that is to make a sprayout panel. To do this, a painter reduces the paint exactly the same way that he or she will when painting the vehicle. Spray it onto a card until the color-hiding indicators are not seen. Then apply clear, just as it will be on the vehicle. After the sprayout panel is dry, the painter compares it to the vehicle. If the color is a blendable match, the painter will be able to produce an invisible repair. If the color is not correct, the formula needs to be tinted.
Gun setup
Proper gun setup and adjustment are also critical factors for a good color match. Color sprayed through a gun with a too-large or too-small nozzle/needle setup can alter color. Guns should be set up specifically for the type of coating to be sprayed. The setup recommendations for sealer, basecoat and clearcoat are often different, and if a painter chooses one setup to spray them, not all of them may be sprayed optimally. To avoid changing setup for each type of coating, painters often have separate guns set up, smaller for basecoats and larger for thicker clearcoats.Finding the proper gun setup may be easy, but still a bit confusing. Paint gun manufacturers' setup recommendations may vary slightly from the paint makers' recommendations. Gun makers' recommendations must be varied enough to accommodate all types of paint, and paint makers' recommendations must vary to suit painters with different types of guns. The most precise recommendations come from paint manufacturers who have specific needle/nozzle setups for their paint and a specific type of gun.
Choosing the blending technique
Yes, even the blending techniques will affect the color of a vehicle. Colors that are difficult to match, such as metallics like silvers, coppers and bronzes, are best suited to "wet-bedding." The area to be blended is first sprayed with a non-pigmented basecoat. Then, when the color is applied, its metallic orientation can be more easily controlled, producing a better match.
Reverse blending (spraying the largest coat on the blend area first, then reducing the size of the spray area with each consecutive coat) also helps with metallic control, making the paint easier to match.
Proper application technique
Proper spray technique is critical to a good match. In fact, even if a painter has done all the above steps properly, but does not have good gun control, the paint result will not be acceptable. Air pressure, gun angles, overlap and flash times all greatly influence the end color and thus the match.Air pressure
With too-low pressure, it is difficult to apply the paint at the proper wetness; and with pressure too high, which is more often the case, the paint has a tendency to be over-wet, making the color darker.
Gun angles and distance
If a painter does not hold the gun perpendicular to the vehicle at all times, the paint could have wet spots, thus darkening the color. The surface of a vehicle is not even. It has high and low areas, corners, flat spots and ridges. Painters must be skilled in keeping gun angles the same as they pass over the entire surface of the paint area. The gun distance is also critical for correct color, as well as the gun's transfer efficiency (how much paint it will deposit on the vehicle).
Overlap
This too is critical to a good color match. For years, decades even, painters overlapped each stroke 50 percent. That is, the second stroke passed over half of the previous one. Guns have changed now, to accommodate the higher solids in coatings. Also, coatings often now have more metallic, mica and other glamour additives in the coatings. With these changes, many paint manufacturers are recommending an overlap of 70 percent to 75 percent. With a greater overlap, the colors cover better with less sticking, mottling, and a smoother paint application. For an invisible repair, the painter must match not only the color, but also the metallic orientation and surface texture — all assuming the repaired surface is first defect-free.Flash time
Flash time, that time needed to let the middle solvents evaporate from a coating, varies with the spray conditions. On hot, dry days, the flash could take less time; on a highly humid day or even just a hot one, the flash time could be longer because the air is filled with moisture, making it difficult for the solvent vapors to evaporate. Air movement also influences flash time, as with a downdraft booth, which often moves such large amounts of air that flash time is reduced. Painters who choose a reducer solely on temperature in a high-air-movement booth will find that the air movement can reduce the flash time so much that color is affected. Often in this type of booth, a slower reducer is better to coordinate with the air movement.
Conclusion
Color matching, one of the most important tasks of a painter, is not only critical, but complex. The process is influenced by so many different conditions that a painter who is aware of them all, and skilled enough to compensate for as many as possible, is a valuable professional. Painters who can perform all the necessary adjustments and produce the successful job quickly and on time are considered not only skilled but highly sought-after.So many factors can go wrong during the painting process that painters must develop special processes for all the varying conditions and situations, to safeguard against difficulties. The more conditions the painter controls, the less often a paint job will have problems. Along with these controls, a painter must master the "eye" and "feel" for painting. Those who do, make undetectable repairs look effortless.
