Kairo: Japan’s Disposable Warming Packs

Heat Release

For centuries, Japanese fended off the cold of winter by heating small stones in a fireplace and wrapping them in silk wadding or cloth to carry around for added warmth. Today, disposable heating packs known as kairo serve the same purpose. Inexpensive and easy to use, they come in a wide variety, including some that can be stuck to clothing or inserted in shoes.

Unlike the traditional stones, kairo warm through a chemical reaction. When a pack is opened, air passes through tiny holes in the outer covering, oxidizing the iron powder inside to create a slow release of heat. Kairo are readily available at such retail outlets as drugstores, convenience stores, and even supermarkets.

(Originally written in English. Banner photo © Pixta.)