Triple milling is a process used to refine particles to the absolute optimal size so they lay better on the skin for superior coverage.
For example, think of how pebbles look in a glass jar compared to sand in a glass jar. The sand looks smoother and more refined than the pebbles. If you hold up a flashlight and try to shine it through each glass jar, you will see the light coming through the holes in the jar filled with pebbles while you are unlikely to see the light shining through the jar filled with sand. This is because light is able to penetrate through the gaps left by the pebbles (larger particles) and is not able to do so when the particles are smaller (sand).
This same principle holds true for makeup. Makeup that is triple-milled will lie more smoothly on the skin and will provide greater coverage than makeup with larger particles. At glo, we begin with the smallest particles available and then triple mill them to ensure that every time you put on our award-winning makeup, it provides even, continuous coverage that lasts!