Safe - sodium acetate (salt, vinegar and water) hand warmer.
Re useable , safe, very effective.
Instructions for use
1. Flex the metal disc inside the Heat Pack until crystals begin to form; the Heat Pack will harden as the liquid inside solidifies.
2. Massage the Heat Pack to evenly disperse the heat.
3. To reuse, place the Heat Pack in a pot of boiling water; place a plate on the bottom of the pot to protect from direct heat. Boil until the Heat Pack appears clear of crystals.
4. Use tongs to safely remove the Heat Pack from the pot. If the Heat Pack reactivates by itself, return to the pot and boil for an extra 3 - 5 minutes.
5. The Heat Pack can be reused straight after boiling by wrapping the pack in a dry towel. When the Heat Pack cools, flex the metal disc to reactivate it.