Aldi/Lidl handwarmers

[Doc]

Aldi or lidl (sorry, I forget which) is offering reusable handwarmers at a low price. You click the metal disc and the solution solidifies, and the latent heat raises the temperature to 55 C.

I wondered exactly how they work, and found this:

Sodium acetate is also used in consumer heating pads or hand warmers and is also used in hot ice. Sodium acetate trihydrate crystals melt at 58 °C, dissolving in their water of crystallization. When they are heated to around 100 °C, and subsequently allowed to cool, the aqueous solution becomes supersaturated. This solution is capable of supercooling to room temperature without forming crystals. By clicking on a metal disc in the heating pad, a nucleation center is formed which causes the solution to crystallize into solid sodium acetate trihydrate again. The bond-forming process of crystallization is exothermic, hence heat is emitted.[3][4][5] The latent heat of fusion is about 264–289 kJ/kg.[6] Unlike some other types of heat packs that depend on irreversible chemical reactions, sodium acetate heat packs can be easily recharged by boiling until all crystals are dissolved. Therefore they can be recycled indefinitely.


Quie impressive, and a good scientific demonstration. Keeps your hands warm too.

 

[woof]

Nice one Doc, how long do they last ?, could be a good thing to leave in the car(on a none flamable pad)to keep it from freezing up.

Rob

 

[Shewie]

Lost me on the technical bit but they are useful sometimes.

Dropped one in my sleeping bag last time I was out and it was quite effective for an hour or so.

 

[Chainsaw]

High school flashback I remember doing supersaturated solutions in chemistry! (try doing supersaturated solutions in a Sean Connery accent ) We have a few of these and the kids take them to school, heats their hands up after the post school snowball fight.

Cheers,

Alan

 

[Melonfish]

they last a fair while tbh, the trick is as you crack the disk massage them furiously until you can't anymore it'll stimulate the gel properly. you can boil em up in the morning when your done too, tho really don't use the same water for your brew *bleh!*

 

[Doc]

In an insulated pocket (or sleeping bag), it'll last an hour or so.

Not as much heat as the solid fuel handwarmers but much more convenient and much cheaper to run.

The tech bit I posted is maybe more complicated than it really is. It takes heat to break up a solid into a liquid, and that heat is called latent heat ('latent' because the heat is used up in changing the state to liquid, rather than raising the temperature) Pressing the metal disc provides a focus for crystallisation, which allows the liquid to solidify again, and you get that heat back.

Sorry, but I'm a bit of a science geek. I'll get my anorak...

 

[Rebel]

I tried them last year and found them pretty useless unfortunately but they are cheap and fun.

The non-reusable ones work much better and the ones that run on lighter fluid (do they still make them?).

 

[scanker]

They're pretty good and last for about an hour I reckon. Nice and safe for the kids to use. I got some years ago - there was a website where they'd send you corporate branded samples - if only I could find it again. I'd agree the lighter fluid ones are better, but a lot more expensive.

You could try here: http://www.emcadgifts.co.uk/default.asp?part=small-heat-pack (found with a google search)

 

[screwball]

I have a costco card and have recently bought a 40 pair box of disposable hand warmers they last for a good 8-10hrs and they are£14-00 a box

 

[Toddy]

I have about a dozen of the reusable sodium acetate trihydrate (SAT), boil to reset, ones, and they are just the bees knees
Just enough of a warmth, no burns, no mess; so easy to use, wake up cold, click a couple, curl round them and drop off back to sleep, nice, soft, no bother.

cheers,
Toddy

 

[greasemonkey]

I've had the reusable type for a few years, I prefer the disposable ones as they last much longer but, like for like, they end up costing much more.

Au Naturale were also selling them last year for £1 each, but they were pink and heart shaped.

 

[deenewcastle]

B&M do these for 79p a pair. I bought a few pairs last year and although I tend to keep a pair on me when out in the cold, they are never intended to be anything other than a brief warm up. I also regularly throw both pairs into my sleeping bag with me when it's cold, just to take the chill off. They are so easy to reboil that it's a no-brainer really

 

[wedgie]

boil em up just before bed an sling em in the sleeping bag without triggering them, after you've dried them. they warm up the sleeping bag nicely then if you get the 3am shivers find em an click the button to warm up a but lol 2 warms for the price of one lol

 

[Black Sheep]

We've got loads of these all different makes and sizes. How long they last depends on size and make.

Got some better one from Millets @ around £7 for a pair and they work well, also the kid's have got some Mr. Men ones from Boots and they're great.

I usually keep a couple in the inside pockets of MOD sleeping bag for the 3am shivers

I also have 3 old lighter fluid hand warmers I use in cold weather but they get too hot to sleep with and stink every thing of lighter fluid.

Richard

 

[helixpteron]

I have a costco card and have recently bought a 40 pair box of disposable hand warmers they last for a good 8-10hrs and they are£14-00 a box

If you pop into the 99p shops, you'll find these little wonders, hand warmer sized (90mm x 70mm) heat relief refill patches (4 per box).

There are also elasticated support 'tube' bandages with two heat pack pockets, which are tailored to fit knees, elbows and wrists, and are supplied with two heat pads.

Self adhesive body warmer sized (130mm x 100mm) heat relief patches (3 per box) which put out over 12 hours heat are in the same display area.

I've given forty boxes of both these types to a group of very badly injured charity volunteers in the last month, and they all report excellent results, so its not just me that thinks that these are an asset, whether its for pain/mobility management, a comforting heat source, or both.

Keep some body and hand warmer types with your PSK, sleeping gear and backpack, because its a whole hell of a lot easier to use these to generate and moderate heat, than it is with brews ups and grub. Keep em' in your vehicles too!