what else besides mylar?

what else could i use besides mylar? i think i saw a cheaper thing called panda something.

white paint is the cheapest and usually the simplest, and quite reflective.

i already put a layer of paint.

White paint!

i third white paint.. either semi-gloss or flat white works great... very cheap and easy, and works great... it is funny how sometimes it is the cheapest of things that work the best in life....

I use panda film on wood frame. If you already have "hard walls" I would use white paint as well.