The idea was to create a sort of stain glass look, with the notable difference of an abscence of dark border lines. The panels are each covered with a thick clear acrylic layer front and back. The clear glossy layers have a partial reflective quality.
When backlit, the light glows through all but the dark black plastic, and fine bright lines can be seen at each interface. Acrylic and UV aren’t friendly, unfortunately, and the plastic would age and discolor in direct sunlight. But artificial backlighting causes no harm.