We have used both foil and plastic vacuum sealed pouches for packaging glassine envelopes prior to storage in the seed bank freezer. Are there major advantages to foil vs. plastic? We have used foil historically, but have also used plastic. The benefits to plastic that I see are not just that it is cheaper, but also that you can customize the size of your pouch more easily. Sometimes we have a very small collection and don't need a full foil pouch and sometimes if we have bulky seeds, it's helpful to make a slightly bigger pouch.