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Sunday, 26 May 2019
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Raw materials & technologies, Production and testing

Control the mottling effect finishes on automotives

Tuesday, 23 October 2012

The first impression, aesthetics, that's the reason to sell a car. Therefore the paint appearance on a car body needs to be extremly perfect. Mottling was until today just a visual evaluation. But only when phenomena can be objectively measured can one control and optimise it.

Measuring mottling of effect coatings on car bodies

Source: Pixelio

Measuring mottling of effect coatings on car bodies

Source: Pixelio

Mottling is an undesirable paint defect of effect coatings. The total colour impression shows irregular areas of lightness variations often descibed as blotchy, non-uniform appearance. As these light-dark spots are quite large, people also refer to them as clouds. Furthermore mottling is not only influenced by the light but also by the viewing conditions and distance.

Objective measurement of mottling

As Gabi Kigle Böckler, Byk Gardner GmbH  in the September issue No 9, Vol 49 2012 (pp14-17) explains, for the ojective evaluation of mottling it is necessary to measure lightness variations over a large sample area and under different detection angles.  Therefore the mottling meter is rolled across the surface for a defined distance. The scan lenght is variable between 10 to 100 cm. The lightness variations are measured point by point.

In order to define customer relevant limits for typical mottling, visual correalation studies were performed and relevant limits established.

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