lukeharris wrote:The unique component of the bags is, I believe, the inner layer of the three--proprietary plastic of some sort. The outer layer is standard poly, and I can't remember the exact composition of the gas barrier between the two plastics--possibly just nitrogen.
It's a three-layer, all-plastic laminate: an interior layer of film such as saran or EVOH that inhibits oxygen transmission, sandwiched between polyethylene layers. There is no "gas" between the layers.
lukeharris wrote: What is particularly outstanding about the bags, in my opinion, is their incredibly low permeability to oxygen and water vapour, as well as their low UV transmission....I would be very surprised if anyone else has a "comparable" product.
I believe you are the victim of misunderstanding, fueled by marketing hype. Any number of companies can probably deliver a plastic film with similar specifications. I say "probably" because GrainPro contradicts itself with widely varying figures for oxygen permeability: 5 cc/m2/day
here and 55.0 cc/m2/day
here.Even if we assume the lower figure (5 cc/m2/day) is more accurate, that performance can be matched or improved upon by other manufacturers. It would be a matter of shopping around to see who has a bag in stock with the right size and properties.
I'm not saying that GrainPro doesn't have a good product. I just doubt the "SuperGrainBag" is unique.