Not too fast. It is possible. You need to get some mold release and coat the optics. Then fill up the area with epoxy, let it set, then remove the optics and clean off all the mold release. Pop the optics back in and your done. OK so there is a little more to it than that but thats the basics. You need to make sure the epoxy is blocked off from the LED and inside pocket of the optic. You also need to make sure there is nothing sticking out from the sides of the optic that would mechanically trap the optic into the epoxy. Let me know if you have any other questions.
That is correct
Make sure you use an epoxy with a high cure to shrink percentage.
That way, when you use your mold release (vasaline works good),
Your optic will have that "Air Gap" that is necessary for
optical refraction. But you could still seal around the very top edge
toward the top of the optic to acheive waterproofness. Mix some
glow powder in there while your at it
Another way to "Fully" pot the optics in epoxy is to use a Silver-Based
solution to coat the outer sides of the optic. That way you can still
have your epoxy completely potted around the optics without optical
distortion. Check with your local mirror and glass companies for some
"Silvering Agent" to do this. I hope that helps!
Robert M.