By Jim Kerr
The autobody paint instructor at our local college in Saskatoon works with new and experienced painters every day, teaching them how to prep the surface, spray on sealers and produce a glossy finish. The most difficult part of painting, however, has to be matching the colour from one panel to another. This can be difficult enough when doing a complete paint job but it becomes a lot more difficult when painting just one panel, such as might be needed in a minor fender bender.
Several things affect the actual colour on your vehicle. Paint changes colour over time; some colours are affected more than others but all are affected by exposure to the sun, small scratches from car washes and chemical pollutants.
The manufacturer of the paint affects colour. When the vehicle is built, the paint used on it is from one supplier, while another supplier might provide the paint to your body shop. The formulas used to mix the paint are different because they use different base colours and additives. For example, some might use more binders to keep the paint uniform or perhaps different amounts of tinter because the base colours are slightly different. The final mixed paint should be close to the vehicle colour, but it is not always a perfect match. Paint only one panel with mismatched paint and it stands out, immediately telling everybody your car has been damaged and repaired.
The type of paint also affects colour. Old cars used lacquer paints that needed polishing after they were sprayed. For many decades we have been using one stage paints that provided the colour and the shine, but many modern vehicles use base coat/clearcoat paints or even tri-coat paint finishes to achieve an attractive finish. Pearls, translucent colours and flip/flop colours add to the matching difficulty. Today, body shops are switching to water-borne paint and again the formulas are slightly different to achieve the same colour.
The final difficulty comes in how the paint is applied. Temperature, humidity, air pressure and the speed of the spray gun all affect the final colour, so with all these difficulties, how is it that body shops can do as good a job matching colour as they can?
First, they start with the paint code for the vehicle. This code will give them the formula to mix the paint but if it looks like your vehicle finish has faded (look at the door jambs compared to the outside) then they can try to match the paint with colour chips. Several manufacturers provide paint chips with holes in the centre. By placing the chip over the vehicles’ paint, the painter can try to find the best match. It is not a perfect method, as faded or non-original finishes may not match perfectly.
Another tool the painter has is to scan the colour with a paint match system. A “gun” is placed on the painted surface and several readings are taken. This is then fed into a computer that provides sample formula that can be mixed up. Stone chips, scratches and dirt are all sampled by this method, so the surface has to be clean and as free of marks as possible to get a good match. Even this method doesn’t always work, so the final steps come down to the skill of the painter.
The painter can spray a sample card and hold it up against the vehicle. If the match looks good, then they use that formula. If the colour is a little off, they can add tinters, and this is where experience and a good eye come into play. It can take several attempts to match the paint, especially if there is a pearl topcoat finish.
For spot or single panel repairs, the painter can also “blend” the paint into adjacent panels. Rather than stopping the new paint at the edge of the repair or panel, the paint is sprayed in a progressively lighter layer onto the adjoining areas. This can then be finished with a clear coat to provide the shine. I have seen custom paint jobs where the colours have morphed from a red into a green with a yellow in between and you couldn’t tell where one colour stops and another starts. Paint schemes like these take a lot of time and skill but it shows off the painters’ true artistic ability.