With kids, if the weather is clear you’re dragged to the park even on freezing days. Kids don’t care about cold. Parents stand still and freeze. Disposable warmers faded by late afternoon. A Hakkin hand warmer (catalytic, lighter-fluid fueled) ran hotter and was still warm at home. Reusable = economical.

Fuel: lighter fluid (benzin)

Sold at home centers/outdoor shops and on Amazon.

Zippo fuel also works, but I use Hakkin fuel to reduce smell/soot and be kind to the catalyst.

Hakkin comes in 3 sizes (L/M/S); most stores carry medium. I use the medium Hakkin Standard. The included measuring cup: 1 cup = ~12 hours; 2 cups = ~24 hours. Twelve hours easily covers a day out; one bottle of fuel gives ~40 refills—similar price to 40 disposable warmers but hotter and longer.

So hot it’ll burn bare skin

Each warmer includes a pouch; use it. Holding it bare nearly burned me—it gets that hot. In the pouch it feels like a normal disposable warmer and is comfy.

Zippo-branded warmers use a similar pouch—very “macho” in black:

Size is like an older iPhone; any small fabric pouch or camera case works. MUJI felt cases fit well (see this blog: http://www.annexia.jp/?p=8645).

My parents already knew about it

I raved to my parents; they said, “Used it when we were kids.” The design looks vintage—turns out Hakkin started in 1923. That’s almost 100 years (2016−1923 = 93). Maybe even great-grandparents used it.

Fueling and lighting take a moment

It’s easy once you know how, but fuel filling feels fiddly until you get used to holding the cup steady. Lighting: under the cap is a catalyst (looks like steel wool). You warm it—don’t burn it—by holding a flame close for a bit. If you burn it, you’ll damage it and need a replacement.

This 1-minute video shows how:

Summary

Eco-friendly, hot, convenient. Fuel + a catalyst that can last 3+ seasons with care; hotter than disposables. Popular with winter anglers/hikers; standing at a playground is also “outdoor.” Many reviewers note the heat output—worth trying.

More on use/history at the official site (very Showa illustrations): http://www.hakukin.co.jp/index.html