Curious about how sodium acetate heat packs work? Sure you are! Here’s a palatable description from WeBringTheHeat.com, a manufacturer of medical heating pads :
A heat pack contains sodium acetate and water. It turns out that sodium acetate is very good at supercooling. It “freezes” at 130 degrees F (54 degrees C), but it is happy to exist as a liquid at a much lower temperature and is extremely stable. Clicking the disk, however, has the ability to force a few molecules to flip to the solid state, and the rest of the liquid then rushes to solidify as well. The temperature of the solidifying liquid jumps up to 130 degrees F in the process.
When you boil the solid, you melt it back to the liquid state. You have to completely melt every crystal, by the way, or the liquid will quickly re-solidify. You can repeat this cycle forever, theoretically, just as you can freeze and melt water as many times as you like.
All of this is mostly too technical for most of us. Let’s just say it’s magic and leave it at that.
Curious how to make your own sodium acetate? Mix 1 part baking soda, 1 part vinegar, and voila! And now that they’ve given you the secret to their heating pads, you can just make your own. But why do all that work when you can buy these heating pads, courtesy WeBringTheHeat.com!
Company says that its products are completely non-toxic, non-allergenic, FDA approved, latex free and have an unlimited shelf life and use life.