Question - What is Mylar, How to use.

Okay, so I have a small Grow-Box that i'm planning on growing Lowryder in, I'm curious to know exactly what I can do with mylar, I know it helps reflect light but does it get hot? Can I use it to keep all light from leaving my box?
-Thanks, thomAs

i would suggest that you don't use mylar. it reflects pretty good, but it is easily ripped/damaged and is pretty fragile. astro-foil is strong, easily cleaned, and pretty much lasts forever. it is also easily manipulated to fit unique positions and shapes.