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Colour matching (spray painting)

The very first question when doing a spray job, is what colour is the car? Of course, one can never have all the colour shades in store because each colour is made up of certain recipes using the three primary colours. Thus, a readable sticker, somwhere in the car, can be very important. Otherwise the documentation from the manufacturer must be consulted, this by the way, is also used by the police to combat crime or to determine the indentity of the car in the case of a hit-and-run accident. Of course, the paint manufacturers also have fast and extensive colour-guide systems.

At this point, the difficult work begins, particularly when the vehicle is somewhat older. Because the shade of the colour changes with time, one must be able to change the direction of the basic colour. A great deal of effort is already being put into the automation of this process. Then, using a suitable scanner, repated runs over a hand-sized, cleaned and slightly polished surface is enough for the computer to determine the mixing formula.

Having a current mixing formula alone, does not mean that the work is over. A well managed mixing area is also necessary. In this area there must be precise scales, clean containers (tins) and the paint must be regularly stirred. To produce the required mixture, mechanical and manual stirring times are stipulated. Metallic paints with lazuring aluminium particles must be given special attention because they tend to fall by the way.

Too little, or rather too much thinner can also spoil a paint job. The specifications given are based on room-temperature. Generally speaking, a test-painting, before the actual spray job begins would be desirable. Another important aspect when comparing colour shades is also, what sort of lighting is available? Neutral daylight, without direct sun rays, will give you the best results. When judging metallic finishes the viewing angle is also important. There is extensive information about which additives can change the shade of this paint when seen from various positions.

In this article, we have left out the preparation work for a spray job and have concentrated only on colours. Thus, the hue can be varied by using either a wet- or dry spray painting procedure, it can also be influenced by temperature, nozzle- and needle setting and even any number of other factors. 03/12