on my boat, with half inch foam core, you could read the name from the inside of the boat on a sunny day.
glass is translucent, regardless of thickness. in most cases if the gel is not there, you will see light through. i could see light
through the bottom seam on a pdq 36. the boat is about 5/8 inch thick there.
while working on spirit of canada, an open 40 from the around alone, we were leaving the shop for the day. with the lights
off in the shop, we could clearly see some one had left on a light in the boat. again through the core.