Japanese Showa era incense burner or hand warmer? Personal equipment

[PBaczuk]

I obtained this over the weekend. Is this an incense prayer item or a hand warmer? Has anyone seen these?

[ghp95134]

Hand warmer. They still made them in the 1970s; the ones now are chemical throw-aways called "kairo".

-- Guy

[Nick Komiya]

This type of hand warmer was introduced in Japan in the late 17th Century and used a slow burning mix of charcoal and high heat retention eggplant ash carried within a perforated metal case. This system predated the principle of using a platinum filament as oxidizing agent for slow combustion of benzine, the standard type of hand warmer employed in the military since the 1920s and WW2. See here for the history of the platinum filament type.

[PBaczuk]

Thank you. So this crude system may be much earlier.

[Nick Komiya]

The idea is much older (this portable type started to be produced around 1904 commercially), but the particular product may not necessarily be an earlier one, as this type is still in production even today. The throw-away chemical warmers invented in the 1970s take the lion's share of the market today, but those products produce water as a byproduct of the chemical reaction, which is problematic for use by astronomers or photographers needing to keep their optics fogging-free even in extreme cold. Thus one make still caters to such niche use.

Also in the days when the platinum type reigned, supply continued for the civilian market, because of the much lower price. By that time, they used waste from hemp fiber production for the heat retention agent (hemp cloth was heavily used for shelter halves and bread bags|), so they were much more affordable for civilian use.