When building or repainting a yacht, having the same colour on the entire yacht is important. But what is colour, why, when and how do we measure this during our inspections?
WHAT is colour?
Colour is a visual perception. It’s dependent on peoples colour sensitivity and environmental conditions such as light. We say that colour perception depends on three main factors: light source, observer and surface condition. Light source and observer are defined by CIE (Commission Internationale de l’Eclairage) and their spectral functions are stored in the spectrophotometers for colour measurement. The only variables left to measure are optical properties of a surface.
To maintain colour in a project, a standard reference needs to be established. The requirement is evaluated in terms of deviation from the standard and not in absolute value. Readings are taken at three different points within a square decimetre and the specular gloss is reported as the average of these readings.
WHY do we measure colour?
- To check and document colour deviations of the various application sessions of the paint on the yacht.
- To document possible colour deviations of the used batches.
- To assess the averages of the colour reading on various surfaces and to document these as a standard that could be used to calculate the deterioration of the colour after one or multiple service seasons.
WHEN do we measure colour?
- The standard reference plate is measured after applied topcoat is cured.
- The general measurements are carried out just before delivery of the yacht, commonly during the final paint survey and after the final coat is fully cured.
- Prior to the completion of the guarantee period of the yacht, often after 11 months of service and again after 23 months.
HOW do we measure colour?
In superyacht painting colour comparison measurements can be done by using a portable sphere spectrophotometer with a spectro-photometer at d/8° geometry. This spectrophotometer measures the amount of light reflected by a coated surface along the wavelength spectrum of visible light. Readings are from the spectrum data.
Absolute and comparative measurements are obtained for colorimetric system L*a*b* following the method of Commission International de l’Eclairage (CIELAB). The lightness value (L*) indicates how light or dark the colour is. The a* value indicates the position on the red-green axis, b* is the position on the yellow-blue axis.
Measured data is viewed under the illuminant observer conditions D65/10, illuminant type D65 standard observer 10°. Simultaneous measurement of both specular-included (colour) and specular excluded (appearance) are carried out to determine the influence of the specular component