The 5 Minute Instant Hand Warmer!




About: I'm a university student from the good ol' USA! I'm studying Electrical Engineering and loving every second of it! I've always been a maker, I love applying the things I learn in school to my projects, and l...

Everybody has seen them, the instant hand warmers sold during the winter months for insane prices. However In this instructable Im going to show you an easy way to make an instant handwarmer with things that you proably have liying around your house!

Its a little odd for me to be posting this in the middle of summer, but in hopes of another stay warm contest I would like to see your feed back to help improve this instructable.

please avoid direct skin contact with the solution! I am by no means a chemist, I do not know how safe this reaction actually is.  I've heard several people say several different things.  Some people claim this produces hydrochloric acid, but I never got burned from touching it.  Whatever is actually happening doesn't matter, please be safe and do not touch the solution or inhale the fumes! Thank you!
EDIT: Published in Popular Science! :D

Step 1: Gather the Materials

There are only 4 things needed to make the handwarmer, all of them are very easy to aquire, if you dont already have them.
*one large ziploc bag
*one smaller ziploc bag
*some calcium chloride ice melter pellets

Thats it!

really it is!

Step 2: Fill the Large Bag With Calcium Chloride

Simply, fill the larger bag with calcium chloride until there is about 1 1/2 inches of it from the bottom. Try not to overfill the bag because it actually could melt through the bottom.

Step 3: Fill the Smaller Bag With Water

Take the smaller bag and fill it about halfway with water, make sure to squeeze out any excess air as this bag will have to be burst in order to activate the hand warmer. Make sure the bag is sealed well to prevent the warmer from activating prematurely.

Step 4: Combine Bags

Put the smaller bag full of water into the larger bag full of calcium chloride, squeeze out the excess air, and there you have it a cheap and verry useful instant hand warmer!

Step 5: Instructions for Use.

The hand warmer is now prepped and ready to be activated, in order to activate the hand warmer, squeeze the smaller bag until it breaks, when the water combines with the calcium chloride it it causes a chemical reaction. A byproduct of this reaction is heat and some gas (I don't know what kind)

*keep all the pellets at the bottom
*put the water bag in with the seal facing down towards the pellets
*seal the bags verry well, you could even glue them shut for a better seal

Tell me what you think!
*leave a comment! PM me!

EDIT: 8/7/09 Fockers sugested an easier way to pop the inner bag without breaking the outer bag, quote: To pop the small bag, just rub the seal and it should slide itself open



    • Big and Small Contest

      Big and Small Contest
    • Toys Contest

      Toys Contest
    • First Time Author

      First Time Author

    60 Discussions


    10 months ago

    Can I use the calcium chloride balls from the kind of plastic dehumidifier box you can buy to put in a damp room?


    1 year ago

    Which type of hand warmers do you recommend and why? Do you recommend
    disposable hand warmers or hand warmers that are filled with lighter
    fluid? The latter type is for example from the brand Zippo.

    Are handwarmers with liquid fuel hotter or cheaper in use than disposable handwarmers?

    And how safe are they?

    Check here

    and advice to me


    1 year ago

    I need to find this info. for a project im doing

    -the balanced chemical reaction equation that you are using in your design

    -the amount of heat given off by the reaction in joules per gram of substance with a cited source
    -the specific heat of the human body with a cited source
    -how much substance you have decided to use in grams
    -a q=mc∆T equation with numbers showing how much the temperature of a human hand would change when given the amount of heat your reaction will produce.

    1 reply

    Reply 1 year ago

    Sounds like great stuff for you to find through experimentation and scientific data collection! Its a simple and safe thing to play with so it should be easy to test.


    1 year ago

    that was a burst of calcium


    1 year ago

    There is some incorrect information that has been mentioned in the comments. Calcium chloride and water do not react to form hydrochloric acid. If it did, DOTs (departments of transportations) would not use as pre-treatment on roads before ice and snow storms.

    Calcium chloride dissociates with water. The equation would be:

    CaCl2 + H2O -> Ca(2+) + 2Cl(-) + H2O

    There is no HCl produced.

    1 reply

    2 years ago

    im in my science class do these hand warmers stay warm long please respond soon as i need the answer soon

    1 reply

    2 years ago

    I'm trying this out for a science experiment in my science class, do you know the measurement in grams for the 1 1/2 inches of calcium chloride in the plastic bag?


    2 years ago

    were can i get calcium chloride ice melter pellets??????

    1 reply

    8 years ago on Introduction

    finally! i am searching ideas for my MRE warmers (i was able to preserve them) and originally thought about 0000 steel wool ground into filings and vinegar.

    1 reply
    junits15Mr Cheeseo

    Reply 9 years ago on Introduction

    The heat output and time is determined by the ammount of CaCl2, simply the mor CaCl2 the more heat and the more time, just becareful not to put too much or you could melt the bag!


    Reply 5 years ago on Introduction

    What about using a glass snapple bottle with lid? Is the gas toxic? When this stuff is no longer heating, what do you do with it?