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Pearlescent Lusters
What are pearlescent lusters?
Pearlescent lusters are platelets of mica which have been coated with titanium oxide and/or iron oxide to give them a color. The color is an interference color. That means that some wavelengths (or colors) bounce off the surface better than others do. If the thickness of a coating is not well controlled, we see a rainbow of colors as in oil slicks and soap bubbles. In fumed glass and pearlescent powders, the thickness of the layer is constant enough to produce a hue to the surface. Under high control, and in multiple layers, they can produce dichroic colors.
The platelets of mica are in the range of 2-100 microns. When attached to the surface of glass, they impart tiny facets which are not perfectly parallel to the over-all surface of the glass. Hence they blur the reflection such that a reflected point of light is seen as fuzzy ball. At first it might be thought that blurring such as this would decrease the information which we see from the surface. On the contrary, this blurring tells our eye more information because, from a single point of light, we get information about the region of the surface which is nearby the reflection of the point of light. When we take a picture of a piece of glass, we are interested in the surface contours of the glass, and not its reflection of the bright lights illuminating the glass. So, pearlescent surfaces provide more information about the surface than shiny smooth surfaces.
