Appearance, along with function, defines most consumer products ranging from faucets to automobiles. However, the appearance of a product can be challenging to communicate and assess. First, there is a vast and inconsistent vocabulary for defining color in the finishing industry. even when everyone is on the same wavelength with the terminology, color itself is subjective. One person’s yellow-gold might be another person’s school bus yellow. The perception of color can also drastically change with lighting, like when you view a product under fluorescent, daylight, or incandescent light. To further complicate things, 10% of the population has some degree of color blindness. Disparities between the perceptions of observers, the orientation of a sample, and changes in general lighting conditions can lead to inconsistent perceptions of color. So how do we create beautiful, consistent colors?
Color challenges in manufacturing
These challenges in quantifying color lead to challenges in manufacturing products. In many cases, the final product must meet a specific uniform color target. Achieving uniformity can be especially difficult for products made of multiple pieces (for example, appliances and mobile electronics), which are often manufactured at different facilities or on different equipment.
As previously mentioned, lighting influences color perception. Natural daylight can produce smooth, vibrant colors while fluorescent lights tend to bring out a specific color, depending on the color temperature of the bulb. Therefore, lighting, including the surroundings that influence reflected light, must be consistent when quantifying color. Trained, qualified inspectors must visually assess color uniformity under controlled lighting conditions. The inspectors’ vision should be qualified with at least a standard color vision test because color blindness is so prevalent.
Texture and orientation also influence color perception. Polished surfaces often appear darker than textured surfaces of the same color, because the eye tends to ignore the highly reflective specular reflections from a shiny surface when judging appearance. The orientation of light sources changes the perception of color. For example, light sources from around a kitchen reflect off the surface angles of a faucet, producing an appearance that changes with viewpoint.
Color measurement instruments
In some cases—to quantify color—using a color measurement instrument can complement or even replace visual inspection for color. Instruments like spectrophotometers can remove the subjectivity out of color measurement. They make it easy to define the color and intensity of the light source. The orientation of the surface relative to the light source and the detector can all be well-defined. A color- measurement instrument can quantify color in a defined “color space”. For example, color is quantified by values for lightness (L*), green to red (a*) and blue to yellow (b*) in the CIELAB color space. These values of L*, a*, and b* were designed to correlate with perceived visual changes in color.
These tools are useful, but in the end, people still need to be part of the process, particularly with complex three-dimensional products. For example, light reflected at shallow angles from curved surfaces can escape from the input aperture of a spectrophotometer undetected, which will at least influence the L* or lightness value.
Manufacturing products with an attractive, uniform look typically requires a well-defined process for quality control that often combines both the human eye and color measurement instruments. For more information about color options and development, as well as the PVD systems that produce them, contact Vapor Technologies today!