I agree about Dartek. It offers the advantage of being "water clear" (of course that also means it doesn't block light if that is a concern). On the other end of the spectrum is HDPE film which is a form of polyethylene that can be effective even when when very thin (commonly .31 to .35 mil). Since is so thin and light it conforms to objects well and doesn't weigh much of anything which can be good. It is also incredibly affordable. One disadvantage is that it is so light (tissue thin) that the normally unnoticed air flow from HVAC ducts can cause move it in some cases!
Both product though do not allow the objects to breath so in some cases you might want to avoid actually sealing them in (in cases where naturally occurring off-gassing can concentrate and effect other components). Obviously old fashioned muslin blocks light and breathes._