First thing, do not mix reflective glass beads into paint or cover them with a clear coat as this will negate or greatly reduce reflectivity. Reflective glass beads must be the first layer to receive light in order to reflect properly.
Secondly, let us talk about retro-reflectivity. Retro-Reflection happens when light enters the bead finds the edge and is returned directly back to the source of the light. Retro-reflection is directional. You only see the reflective glass beads reflect when your eyes are at the same level or in between the light source and the glass beads. Think of it like this: You see the signs reflecting on the interstate and roads because your eyes are at the same level as your headlights. If you were riding 15 feet above your cars headlights, you would not see the same reflectiveness. Factors that affect reflectivity (refractive index) are clarity, roundness and inclusions or air bubbles. In addition, the brightness of the light source obviously can affect how well the glass beads reflect. The size of the reflective glass bead mainly affects the angles that you can see reflectivity. One final note, do not push the beads down into the medium (paint, glue) just sprinkle on top and let the medium dry. If glass beads are pushed down too far into the medium, they will not reflect as well. Hope that helps! https://colesafety.com or https:reflectivebeads.com