The connection between foam color and density
There is a strong correlation between the intensity of a color of a foam, and the density of that foam. It is often experienced that the color is paler and lighter for a foam with low density (let’s say 30 kg/m3), compared to a higher density (for example 100 kg/m3). When a color is matched to the Pantone palette, the density range where the desired color will be indeed, always has to be kept in mind.
The reason behind this phenomenon is that the pigments used for coloring are very small particles and the distance between the particles determines how intense a color is. If the distance is big, the color is paler and lighter, if small, the color is deeper, more intense. When foaming, the plastic material is expanded and because of the increase in volume, these pigments are moving farther away from each other. In a foam with 30 kg/m3 density the distance is bigger than in a 100 kg/m3 density foam.