How to seal material against helium/hydrogen leakage?

Question

What is the best light weight fabric-like material for creating balloons designed for lifting heavy loads? For example weather balloons or modern blimps? Also is there any kind of spray on liquid product that can help seal containers from hydrogen leakage because I know hydrogen can leak out of anything, even solid metal containers.

Thanks

Answer 1

Hydrogen is one of the most Difficult Materilas to prevent it's leakage , due to it's small molecular size .  There is more than a school when talking about such insulation , so check the one u prefer from the following links :

Answer 2

Mylar or aluminum foil. Some people make impressive UFO's with balsa wood frames and aluminum foil, and fill with H or He. As for a spray-on product see the patent link, but like most patents I don't know if it is really doable.