Have you ever noticed that in many cases the color of a vehicle’s bumpers doesn’t exactly match the color of the vehicle body? I noticed this recently on one of my own cars after the bumper was painted by a body shop as a result of a minor parking lot fender bender. The repainted rear bumper was, to me, clearly a different color than the rest of the body. This color disparity heightened my awareness of the issue – to the point where I see it on all types of cars everywhere I go. So, I started to dig in to the issue, trying to find out what causes it and, more importantly, how we can limit the issue all together here at Automotive Quality Solutions.
My initial thought was that the body shop performing the repairs on my car either didn’t mix the paint correctly, or chose the wrong color variant. Every vehicle color has a particular code designation. For example, the paint code on my car is NH701M (found on a sticker inside the driver’s side door jamb). An auto body shop would type this code into a computer software and would receive a list of tints and dyes to mix together to re-create the original factory color. Seems easy enough, right? Well, not always. Vehicle manufacturers mix large volumes of paint for spraying vehicles on a particular assembly line. Yet what happens if the manufacturer has multiple assembly lines, or if they have to mix a new batch of paint? Variance. That is, even vehicles painted by the factory with the same paint code can have slightly different colors. Manufacturers periodically publish the formulas for mixing variants using somewhat cryptic descriptors such as, “darker”, “lighter”, “yellower”, “dirtier”, etc. So it is then up to the body shop to determine which color variant is closest to the original factory color of the vehicle. But what about an older vehicle on which the original factory paint is slightly faded? Painting the a repair area with the original factory color clearly won’t match the existing paint in this case. So, in the case of variants, or aged paint, it is up to the body shop to determine the best color to spray. This is done by mixing a batch of paint and spraying a small test card. Once the paint dries on the test card, it is held up next to the vehicle to see if the color matches. The painter determines if a new variant should be mixed, or if adding different tints will match the existing paint.
So, now let’s say that the body shop has determined the best color match and they spray the new or repaired bumper cover on my car – but the color still doesn’t match! Well, then we need to look at the substrate (the surface that we are painting). Most of the vehicle surface is metal whereas the bumper covers, mirror covers, mud guards, etc., are all plastic. Applying the same paint on plastic and metal can often result in a slightly different color appearance. This can be due to several factors. First, the plastic dissipates heat more slowly than metal (the paint dries slower), and drying time can be a key factor in paint appearance. As paint dries more slowly, metal flakes in the paint have more time to settle at different angles, and volatile chemicals have more time to evaporate – causing slight variance in the paint color. Another factor is that plastic can hold more static electricity charge than metal and, if not properly discharged before spraying, can cause metal flakes to align differently than on a metal surface. Substrate differences require different spraying techniques to minimize paint color variations.
Well, now we have the color matched and we’ll use different spraying techniques to minimize the difference between the factory paint and the newly sprayed paint – the color must surely match now! Not necessarily. Most modern factories use electrostatic spray equipment to paint the metal surfaces of an automobile. While they use conventional spray equipment to paint the plastic surfaces. So, even vehicles coming off of the factory line can have slight variations in color due to the differences in spray equipment.
And even accounting for all of these differences, colors can still seem slightly different simply due to the way light reflects and refracts off of curved surfaces (like a bumper) versus the relatively flat surfaces of the doors and hood.
At AQS we’ve learned to take all of these factors into account when painting a repaired surface. First, we take the time to properly prepare the repaired surface for painting. Next, we research, formulate, and mix our tints and dyes with a computer controlled mixing system. We then spray test cards to find the exact color match. Finally, we alter our spray techniques to account for environmental conditions (such as humidity and air temperature), and will often blend the new paint into the existing factory paint of neighboring panels. All of this to ensure that the final repair is seamless and invisible.
We believe that if we take a few extra minutes to properly repair and prepare a surface, and take the time to really find the exact color match, we save time and money in the long run by not having to repaint a surface multiple times.
Now if I can just get the body shop that originally repaired my bumper to read this article!