Handwarmer expire dates.

[WhatToHunt]

It’s an iron compound that oxidizes. Exposure to air starts it and cutting off air can slow it down or even stop it but it is a finite process. Once all the iron reacts, they are done. Pin holes in the wrapper will start the process. Those rock hard ones are fully oxidized due to faulty or compromised packaging. I imagine the packing and glue degrades over time and that’s probably why they expire.

Related to cutting off the air: I've recently started putting them in a ziploc bag to get several uses out of them (a little trick my dad taught me). So if I only used the warmer a few hours, when done hunting just ziploc it (making sure to press out as much air as possible) and reopen for use for my next outing. I've only tested this with a few days between each use and only up to three uses. This is with the Hot Hands Super Warmers which I highly recommend.

 

[miller6212]

I’ve had some that were expired a couple years but they either didn’t work at all, didn’t get very warm, or didn’t stay warm for very long. Big difference when I also had some brand new unexpired ones at the same time.

 

[ninja master]

Air is key

 

[roosiebull]

It’s an iron compound that oxidizes. Exposure to air starts it and cutting off air can slow it down or even stop it but it is a finite process. Once all the iron reacts, they are done. Pin holes in the wrapper will start the process. Those rock hard ones are fully oxidized due to faulty or compromised packaging. I imagine the packing and glue degrades over time and that’s probably why they expire.

I wonder if you could pile up the ones you didn’t use and vac pack them until the following year

I saw some in a dresser of mine that have to be 15yrs old, no clue what shape they are in, but I’m curious now, they are a couple individual packs of hothands brand

Another thing that could be incorporated is put them in a big canning jar, fill 3/4 with hand warmers, maybe a piece of foil, light a chunk of wax paper and seal the jar. We used to do that with salmon eggs we didn’t use that year and it really seems to kill the oxygen, very little freezer burn doing that

 

[doverpack12]

I’ve had pretty good luck past expiration.

Costco has been out all year so I got some grabber hand warmers and holy smokes do those get HOT and last…

If I know it’s going to be really cold I’ll use a toe warmer in my mittens because more readily available air makes them crank some heat. Of course they don’t last as long either.

 

[Voyageur]

I have used some I found in my Dad's hunting closet that were ridiculously old....possibly 30 years or more. They heated up just fine for me. I did do some research before trusting them in the field and seem to remember reading that as long as the contents weren't hardened/crunchy (as previously stated) they were fine.
Hope this helps.

 

[Blockcaver]

Always heard they were iron filings and salt…add oxygen (air) and you get heat, along with oxidized iron…..just like your truck in the northern states

 

[Marko]

Related to cutting off the air: I've recently started putting them in a ziploc bag to get several uses out of them (a little trick my dad taught me). So if I only used the warmer a few hours, when done hunting just ziploc it (making sure to press out as much air as possible) and reopen for use for my next outing. I've only tested this with a few days between each use and only up to three uses. This is with the Hot Hands Super Warmers which I highly recommend.

Whattohunt, l like the sound of that! Thanks for that tip, it seems foolish to waste them.