These say "self-activating".

Take a look at the bottom right corner just to the left of the 6 pairs wording. Says Air activated. The hand warmers that my golf shop sells are activated by shaking. I will take a look at the brand tomorrow.

I'm sure they are air activated but from the posts it seemed like you were looking for the ones that @pyze-guy mentioned and those are them.

Chemical warmers that use other ways to warm up exist but it seems that they don't get as hot nor last as long as air activated warmers up to 2hrs vs 6hr more or less

Why Do Hand Warmers Heat Up When Exposed to Air?
http://www.wisegeek.org/why-do-hand-...sed-to-air.htm
https://en.wikipedia.org/wiki/Hand_warmer

One they don't talk about here is the icepack in the microwave

Those are self activating.

I got my battery heated socks from eBay last week. I bought the cheap stuff (30$ shipping included) just to try it out.
Without surprise the cheap stuff is cheaply made, it's 80% cotton, too tight and the heating element felt too weak to overcome the cotton factor.
So I tried something that in the worst case would waste my 30$ cheap heating sock, I managed to removed the elements from the socks without breaking them and put them between 2 layers of aluminum tape use for heating duct repairs and I tape them over thin syntetic socks and put thick wool socks on top of that. It's now working, This morning at -28° celcius my feet were still warm after a 27.4 kms ride.
Way better (for me) than chemical warmers.

Recently I used toe warmers on the top of my shoe under a shoe cover and they worked well

brilliant! got a picture?

There's two pics. You can see that after only 3 use the foil tape is already tearing up so it may not last long. I'll try to find something to make it stronger so the heating element won't break.http://bikeforums.net/attachment.php...hmentid=355616http://bikeforums.net/attachment.php...hmentid=355617

hmmm OK interesting!

I went from 'brilliant' to 'interesting', I can't wait for 'WTF!!!' :lol:

As you can see in theory the plan is almost perfect, in real there's room for improvement. It may also be a bad idea from the start. At least I know that heating socks or insole can produce enough heat to keep my feet warm at -28°celcius for a 1h50 ride , which I never achieved at - 15° with chemical warmers.

ok. WTF.

no, jk dude...

what if you were able to cut an insulated food bag, the type you'd buy at your larger modern supermarket, and form a partial sock with that? or, even a piece to simply layer over the instep, down your foot, over and then under your toes? maybe even removing the insulation from an insulated water bottle?


also: http://www.uline.com/Product/Detail/...g&gclsrc=aw.ds