Instant hand warmers are great--just shake 'em up, and you've got spontaneous warmth to thaw your hands during the cold winter months. But they're awfully expensive, and not because they're complicated to manufacture. In fact, you can make them yourself in a few very easy steps.
1. Fill a large ziplock bag one quarter of the way full with calcium chloride ice-melt pellets (available at most hardware stores).
2. Fill a smaller ziplock bag halfway with water, close tight, and place inside the first bag.
3. Squeeze the smaller bag until it breaks open, to create a heat-producing reaction between 20 minutes and an hour.
Originally posted by Justin DiPlacido on Instructables.
As a concerned scientist I would suggest searching google for the MSDS for Calcium Chloride, It can be quite nasty if handled improperly. Be sure to avoid eye contact or direct skin exposure, this may cause a mild to severe skin irritation. Calcium chloride and water react exothermically, so if your hands are wet the reaction will take place on the wet area. Wear gloves and avoid the vapors. Safety First, then teamwork
thanks for the warning
as a person i'd like to note that this stuff hasn't killed me yet. my grade school used to use this stuff on the playground so we would be around it constantly, i have a not so fond memory of seeing what would happen if i shoved one of these pellets up my nose. to say it hurt was an understatement but i don't think it could have been life threatening unless you diligently use more than what you actually need.
we need balance, safety is a good thing but too much makes you paranoid, and while some things require the full fume hood and scrubber not everything does.
to mars or bust!
I realize calcium chloride can be dangerous but if you look at half of the MSDS' out there for normal, everyday things you'd be terrified to leave the house. Look at the one for sodium chloride and you'd think you should wear a facemask before you salt your steak. I understand the need for MSDS sheets, especially when handling these items in large amounts but I wouldn't worry too much about the little bit being used for this hand warmer.
It may be that one product is more hazardous than the other.
Seem the flake stuff has a pretty tame msds while the anhydrous version has a bit more precautions.
I use the reusable hand warmers from Hotsnapz.com for my class experiments. Based on the supersaturated solution of sodium acetate and water, this salt is a bit more friendly should the pouch puncture. Highly recommend them for scientific studies on supersaturated solutions, calorimetry, crystallization and other experiments. Also, if your are a science teacher or school, you can call the owner to receive science instructor discount which really helps.
Not trying to be mean here, but starting an exothermic chemical reaction in a zip-lock bag is plain foolish, especially without even considering the chemicals being produced in the reaction.
If you're here to learn a diy for a hand-warmer, don't listen to the people that say this is relatively safe. You should know that the solution will become hydrochloric acid.
This means that it will burn you and almost everything else you spill it on. It will also burn through your zip-lock in a matter of time dependent upon your mixture and how much you shake it.
Hydrochloric acid is not for the skin. It can eat concrete and metal. Read about it before you consider trying this - and then learn about this reaction instead of measuring chemicals by the "1/4 full" and "half-full" sandwich bag. For those of you saying this is relatively safe - learn everything about a chemical reaction before you recommend it to others!
Idjot, t has little to do with the acid involved and a LOT more to do with the concentrations involved. Acetic acid (in some concentrations we call it vinegar) can be a pH of 2.3 while hydrochloric acid can be 2.0. The same with citric acid. And it can do every single thing you mention too. So just picking out one of the by products without considering the concentrations of that by product is pointless - much like ajohnson pointed out with salt.