I have not looked closely at the lid seal. I do not want to open my vest pack today, but will look at the opened one I have at home. My guess is that this seal is a teflon film covered product. Iodine vapor is very corrosive to metals, and can easily penetrate most plastics or paper seals. Many plastics also allow water vapor to slowly penetrate the container which degrades the tablets also.

There are some old threads here about various attempts to package the iodine tablets in other than glass containers. I cannot remember the results of all, but someone had used a cutoff Bic pen and I think a test was arranged to see if the tablets after a certain amount of time still contained active iodine. Foggy mind here.....need another old hand to chime in.

Plastic drinking straws, metal tubes, plastic wrap etc have all been discussed in the past. Great reading from inventive minds, try a search with the parameters set to "All Posts" on iodine....that should give you some idea of the attempts and experiments done by others.

I continue to carry mine unopened in their original packaging as my best plan. My primary reason to do this is my belief that if I need to chemically purify water, I will want the capability to do a bare minimum of 3 gallons....~12L which is 24 tablets. This can be added to a small kit in a small bottle, but I have chosen to double this and carry the whole original bottle.

Potable Aqua is only one way to purify with fairly limited volumes. My preference in my larger kits is a mechanical pump backed up with pure iodine crystals (Polar Pure), these together will treat hundreds of liters of water. With a decent fire kit and a boiling vessel I am in fat city. My vest kit, consists of a 1/2L bag and the 50 PA, which I would hope to be able to backup with my larger kits or boiling.