I had a customer today ask about the folding of the bags and whether it damages them. Definitely understandable, as there is some creasing of the bags when folded. I asked her to try to do a seal test to determine the integrity of her bags. She sealed a bag and submerged it in water to see if there were any leaks…happily for me, there weren’t!
The Mylar bags we sell are actually a multi-layer combination of foil, PET (a type of plastic) and LLDPE (another type of plastic). The two plastic layers are the oxygen barriers and enable heat sealing…the foil is mainly for stability and keeping out light. All foil bags also have ‘pinholes’ in them (up to and including the heavy duty 7-8mil bags), however they do not effect the integrity of the bag because it is the other layers that are really keeping the air in and out of the bags.