I was looking ay fiberglass resin, seems a lot cheaper, then the polyester casting resin at the art store. So was wondering if fiberglass would be better for casting a helmet or would polyester be better
I think I understand what you are trying to accomplish. Any uncoated lens that would allow light to enter on one side would also be transparent to light coming back the other way. Coatings would make a difference but you would not gain the extra amount of lighting you are trying to obtain. However, if your lens is surrounded by reflective material, then any stray light could be redirected back to the panel.
Photo-electric or Optical: These are more expensive but more effective at detecting larger particles of smoke produced by slow-burning fires, such as smouldering foam-filled upholstery and overheated PVC wiring. They are marginally less sensitive to free burning flaming fires.
