I have a possible source on glass vials, but I don't think they have teflon caps. Has anyone tried using teflon plumbing tape over the mouth of the glass vial to protect the cap?

Not teflon tape, but...

I am currently researching the foil-lined seals from the top of orange juice bottles. No, really. Here in New Zealand, orange juice is available in 1 litre and 3 litre plastic bottles. There is a lid on the bottle. Underneath the lid is a dense foam seal which is heat-welded to the mouth of the bottle. The seal is about 1" in diameter, with 3 small tabs around the circumference. The seal is peeled off and discarded when you want to open the bottle, and of course the lid can be screwed back on afterwards.

The seal material is dense foam, about 1mm thick, with a foil underside. I think the foil is coated with polythene. I took a 10mm punch and punched a circle out of the seal, and inserted it into the lid of a small vial. The vial lid already had a small disc of dense foam as its original seal. My premise was that the foil would be a good block for iodine, even though the polythene layer might absorb some. I assumed that the existing foam disc in the cap would add more spring pressure to the foil/foam disc and allow an even seal around the mouth of the vial.

I did this about a month ago, and the result is pretty good.

The first time I re-packed the tablets (I am using Potable Aqua) I used only the original foam disc seal in the vial lid. It soon went brown, and other things that were packed next to the vial started to become affected by iodine vapour (e.g. the chrome top on my mini BIC started to corrode).

So, I got a new lid with a new insert and added the punched disc from the orange juice seal. For your delight, ladies and gentlemen, I have just now removed the cap and examined it. It is true there are some brown circles which mark the outline of the mouth of the vial, but! The original foam insert can be seen at the edge of the new foil insert, and it is still white. Iodine vapour would make it brown, and it would be obvious. I will call it success!!

The only improvement I would make is to use a bigger punch. The mouth of the vial is about 10mm, so my disc has to be placed carefully on top. The inside of the lid is about 11mm or more in diameter (to accommodate the screw threads on the vial) so it is possible that the foil seal would move wrt to the mouth as the lid is tightened.

I think that a disc of heavy foil would also work, with the springiness of the original insert behind it to give a good seal. I think that teflon tape, even though it is impervious to the iodine vapour, would be too fiddly to use, and would be destroyed by the action of screwing down the cap.

Whew! That was a long post. I hope it made sense.

So.... use the tape to cover the mouth, then use a foam pad to protect and press on the tape? Maybe tape, foam, then another layer of tape? The tape might not be vapro tight for more than two openings, but a wrap of tape around the edge.... I've got a lot of teflon tape. :P

I'm looking to repack for a PSK- if I have to open this, I'm either needing the tabs or I'm repacking them. I'd love to go with the new flat pack guys, but I can't find them around here. When I find them, the price is awfully high.

I tried plumbing tape but still had leakage around the cap. The iodine vapors were starting to corrode some of the metal in my PSK. I found that 2 layers of electrical tape around the outside overlapping the cap and the bottle, prevented any vapor leakage. The tape should be replaced once a year.

You know Doug has a page with a source for glass vials with teflon caps, right? It's linked from the other iodine tab thread from a day or so ago.

Yep. But they aren't just for me, and I've got a lead on some bottles that a bit smaller. They'll work better for some of the guys I'm talking with who are looking for these pre-deployment. I've also been able to find some teflon disks that should be a little larger than the mouths of the bottles, so they will work as seals.

I need about 50 sets total. For 40 buck I can get these guys, and if they don't work, so be it. I can find use for 100 small glass vials. Premixed magnesium and aluminum flake, with a little bit of black powder for ignition, anyone? Pour out a quarter's worth of that, and add some sparks, should light about any tinder I can think of, rain or shine. :P

You may want to add some iron oxide if you want thermite. As for small vials, I have been dipping the cap area in a can of tool handle liquid. This is some kind of plastic/rubber dissolved in a solvent. You dip the tool handle into the can & when the material dries, you have a rubbery tool handle.
Turn the vial upside down & dip. The plastic stuff dries & covers the cap/neck area with a continuous layer of rubbery material.

Might want to re-think that "rubbery tool handle" trick. The one I use, Plasti-dip, does a great job in many applications. BUT..and a BIG BUT..: it must be somewhat gas permeable because in a Zippo lighter so dipped the fuel evaporated anyway. And iodine tablets in a soda straw..totally dipped in multi-layers of Plasti-dip outgassed and corroded nearby metal anyway.
I couldn't believe this, because the plasti-dip did create an evidently waterproof seal. But lighter fluid and iodine got through it.

Yeah, but aluminium and magesium are just metal flakes.

Add iron oxide, and you have thermite! Might get a few higher raised eyebrows if it has to go through a security check point.

Well, here we are almost 2 years later and the seal has failed. I haven't looked at my PSK for a while, and I am now living in Japan. I do carry it, but I just opened it and the iodine has escaped and made a few of the surrounding items brown. I'm not sure of the shelf life of Potable Aqua. Maybe I should have replaced it by now, in which case a failed seal would be no problem. None of the other items are damaged- just brown. That will dissipate over the next few weeks.

So, I shall need to replace my Potable Aqua tabs. Any more ideas?

A

(I now covet the Steripen, but that deserves a thread of its own, and besides, it's too large to fit in a tin with all the other stuff).