In the paint department, refinishing a panel — or refinishing a panel that has a repair in an adjacent panel — is one of the most common paint procedures performed. And with today’s highly complex colors having metallics, pearls and combinations of color enhancements, the technician’s job of matching colors has become very difficult. To meet this challenge, several paint techniques have been developed to blend the new color (Fig 1) into the old color. If the match is slightly less than perfect, the eye is tricked into not seeing the subtle changes. In fact, many paint companies recommend that all repairs be blended to speed productivity. Although some painters still panel paint colors to ensure color will match, "blend-it-and-send-it” has become the standard.
Color match issues
Though manufacturers standardize all their color formulas, not every factory-painted car precisely matches that color standard. If a color is applied at multiple manufacturing locations, each location may have a slightly differing color tone. Though paint companies try very hard to identify and correct their formulas for that variance, it is not always exact. Many paint manufacturers provide variance decks (Fig 2) to help match the more common color variations, which has become very helpful. By comparing the variable formulas to the vehicles color a “blendable match” can often be found.
There are also many other possibilities that may cause the color to be off. As examples, over- or under-pouring when mixing the formula, poor spray gun adjustment or improper spray technique, improper reduction, even mixing to the incorrect formula, or a corrupt toner deck—can each cause mismatch.
If the painter is familiar with and confident that the color that is being applied is one that will match the color, then mixing and blending the color with the fastest blending technique (such as the "Standard” blending" technique) will usually produce a satisfactory match. (More on blending techniques later.) However, if the color is a difficult one or one that the painter has had trouble with in the past, the best method to tell if the color will be a blendable match is to make a spray-out-panel (Fig-3). By spraying a panel with the color that is to be applied to the vehicle, then comparing it to the vehicle (Fig 4), the painter can determine whether the color is blendable or not.
Clean-Clean-Clean
Huh, you say? You are correct: cleaning the vehicle has nothing to do with the color match of a blend. But it can be very frustrating to put in all the time and consideration on the vehicle’s color and blend technique and then notice multiple dirt nibs that must be corrected before delivery.
Here are some quick tips on paint job cleaning. Clean the booth before each paint job; blow down the wall with the fans on before the vehicle is loaded. Mask as much of the vehicle as possible outside the booth, then blow the vehicle off and load it into the booth. Once in, finish any masking such as final bagging. Next chemically clean according to the type of paint system that is been used. Once the vehicle is in the booth, the fan should be on and the doors closed. At this point access to the booth should be limited and the doors only opened when necessary. Also, the booth should be balanced to a slightly positive air flow (Fig 5) so if the door must be opened, dust will be blown out and not sucked in.
Next, tack off the area to be painted with a new tack cloth, and then with a second one. Tack off the masking paper surrounding the paint area, and just before painting the vehicle, tack the air hose off so random dust that it may have picked up will not drop into the paint.
All these precautions that can be taken prior to applying the blend will pay in less detailing or even avoiding a repair that may otherwise be needed just because of dirt.
Blending techniques
While I am sure there are many variations on the three types of blending that will be discussed here, I’ll review these techniques that most often used: Standard blending, Reverse blending, and Wet-bed blending.
Standard blending
As paint colors became more sophisticated and with it the problem of mismatched colors when panel-blending was used, painters decided to extend the new paint into the old color. Multiple coats were used (3 to 4) with the first coat, which was extended 4 to 6 inches into the old panel. The next coat was extended 4 to 6 inches beyond that, and the third also extended beyond the second (Fig 6). After the repair and blend area is sprayed to full coverage, it is best to use a color-corrected light to check that all areas are fully covered, especially tricky areas such as fender edges and recessed areas that may not have been sprayed directly.
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Tech Tip: Though the booth should have color corrected lights, many painters like to turn the booth lights off and use a separate color corrected light to check the color of for both color match and full coverage. Often with the booth light on, shadows are cast that may hide thin paint. The defect then may not be seen until the vehicle is out in the sun. |
The painter should also consider the areas where the blend ends, especially on the final coat. (This goes for all the spray techniques.) If the blend is ended abruptly in a straight up and down line, it is more likely to be seen; so if the blend is instead staggered or done at an angle, the blend’s end point is less likely to be noticed. The car’s design, or where shadows naturally fall, can be used to the blend’s advantage. Ending the blend in a staggered line under where the side mirror normally casts a shadow also helps hide a blend.
Gun technique and the blend
Though gun technique is important in all painting, the blend has some of its own challenges, not the least of which is overlap. For years, a 50% overlap was sufficient to cover without streaking the paint; but as highly metallic colors became even more popular, painters found that a fuller coverage was needed and most paint manufacturers and paint gun makers now suggest a 75% overlap is better. Also, it was found that many painters tended to fan the gun (Fig 7) at the end of the blend; unfortunately, this would cause the metallics to orient incorrectly and cause a visible line, sometimes referred to as a "halo". To combat the poor orientation, it is better to keep the gun perpendicular to the paint surface and off-trigger the gun. This can be a bit tricky at first, but with practice the skill of slowly letting the trigger off prevents the problem. The metallics orient correctly because the distance to the surface is correct.
Reverse blending
The Reverse blend was developed to combat the problems listed above. As colors such as silver, gold, and bronze, for examples, became even more difficult to spray, the reverse blend was developed.
Though the reverse blend overlaps each coat by about 4 inches, the same as the standard blend, the difference is that the first coat is the one that extends the farthest: 12 to 14 inches into the adjacent panel. The second coat is blended four inches less, and the third yet four inches less than the second (Fig 8). The same techniques as the staggered blend line, 75% overlap, and off-triggering should be used with this technique.
To combat problems such as halo, visible blend line, and poor metallic orientation, paint manufacturers developed products often referred to as the orientation coat. One of the problems that occurred with highly metallic colors, such as silver, is that the metallic flake would gather in even small scratches left when prepping the panel to be blended. These metallic streaks could not be corrected with detailing, and would need to be re-sprayed.
A clear orientation coating was developed that could be sprayed onto the panel being blended to keep metallics from gathering; painters found that halos were also reduced with an orientation coat. Thus the Wet-bed blending technique was developed.
Wet-bed blending
To use the wet-bed blending technique, the painter sprays a full wet coat of orientation, or wet bed, over the entire panel to be blended. Then the color is applied using the reverse method (Fig-9). This technique allows the color to be sprayed onto a tacky surface where any small scratches have been filled with the orientation coat, and the metallic will orient correctly. Halos, though not always eliminated, are markedly reduced.
Don't become careless with prep, thinking that the orientation coating will cover scratches. Though it does help stop metallic streaking, good prep (especially with waterborne basecoats) cannot be overlooked. Follow all the paint manufacturer’s recommendations for the proper surface preparation for the paint system that you are using.
Sealers and blending
Many painters use a sealer when painting. These can cause problems when blending, though. If the sealer gets on the panel to be blended, it tends to leave dry spray that is not corrected with orientation coat. Though some painters use gun control (angling the sealer gun away from the blend panel), the safest way to avoid the problem is to temporarily mask the blend panel until the sealer is applied, then unmask it and apply the blending technique that you believe to be best for the application. Remember: tack often and thoroughly to eliminate dust and dirt. Also, “pay it forward.” If you notice a defect, stop and correct it before going on. De-nib when you can, and keep the paint surface and booth as clean as possible.
Which technique to use?
All three techniques have their place for specific paint applications. One of the tasks of a lead painter is to choose the fastest, least expensive method in both materials and time, for each paint job. For simple non-metallic paints that have a history of blending with little or no difficulty, the standard blend technique may be the best and fastest. With other, more sophisticated colors, the reverse technique may eliminate the problems that come with this type of color. Lastly, for those jobs that have a history of difficulty the wet bed should be employed.
As lead painters, use your experience to decide when and which special techniques you should use in spraying difficult colors.
