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Object in focus: self-heating cocoa tin

This post is the first in a new occasional series in this blog: Object in Focus. Members of the Polar Museum team will write about an object from our collection that interests them – it could be big or small, Arctic or Antarctic, famous or obscure, on display or buried in our stores … anything that has caught our eye recently and that we’d like to share with you! I’m going to kick off with a real oddity that I discovered while we were doing a practice condition survey for this season’s UKAHT team: the self-heating cocoa tin.

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Yes, it is a tin of Heinz “cocoa milk” that can heat up inside the tin, giving you a hot drink in minutes without the need for a separate fire or heater.

The tins were developed by Heinz in the early 1940s. The range included six types of soup (oxtail, kidney, cream of chicken, cream of celery, cream of green pea, and mock turtle), malt milk and cocoa milk. The idea of the self-heating tin was not new – for example, here is a patent from 1907 for a self-heating tin invented by the Aetna Self-Heating Company (you can see a replica of the original tins here). These earlier tins had a chamber filled with calcium oxide (quicklime), which produces a great deal of of heat when mixed with water. However, the Heinz versions used a different mechanism that had been invented and patented by the chemical company ICI. Inside the tin was a tube filled with smokeless fuel (some sources say cordite!) that was ignited with a fuse at the top of the tin. Within 4 minutes, the tin and its contents were piping hot and could be poured out. Anyone could have a hot meal without cooking apparatus.

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The British Army included self-heating tins in soldiers’ ration packs for the first time during the Normandy landings of June 1944. They must have seemed like an attractive proposition: hot food for tired troops who were waiting in tense and uncertain situations, without the need for fires that could give away their position to the enemy. The reality was somewhat different, however. If the instructions were not followed absolutely to the letter, then the tins could burst or even explode, showering you with the hot contents.

Here’s Sophie reading the rather terrifying-sounding instructions on the back of our tin:

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They say:

SELF-HEATING CAN

INSTRUCTIONS FOR USE

SHAKE CAN. PIERCE TWO HOLES IN LID ABOVE ARROWS

LEVER OFF CENTRE CAP. LIGHT WICK. WAIT FIVE MINUTES.

CONTENTS THEN HOT.

ALWAYS PIERCE CAN BEFORE LIGHTING WICK

 

The underlined instructions were absolutely crucial if the tins were to be used safely – and, unfortunately, they weren’t always. Soldiers were often careless with the instructions, lighting the wick prematurely, or with a cigarette, or not punching the holes correctly. One veteran, Ray Eaglen, remembers being issued with these tins by the British Army in 1944, when he was sent to France during the Normandy landings:

“Hundreds of soldiers were packed into the Liberty Ships like sardines. There was scarcely room to sleep, sanitary arrangements were primitive and there was little in the way of food. At one stage we were issued with army biscuits and cans of self-heating soup. One lighted a touch paper in the top of the can and after a while a hot can of soup was produced, at least that was the theory. From time to time unfortunately, we had cans which exploded, showering hot soup on anyone within range.”

Another soldier, Lawrence McHugh, remembers a colleague getting hot tomato soup in his ears because he had punched the tin in the sides rather than the top!

This film footage from the Imperial War Museum shows soldiers waiting to depart for Normandy prior to the D-day landings. Right at the end of the film (at about 3 minutes and 15 seconds), you can see one of these self-heating tins in use, being lit with a Swan Vesta match. Unfortunately, the film ends before we see if the outcome was a lovely warm drink of cocoa milk or a scalded ear…

Our tins (we have two, both of cocoa milk) date from a bit later than the second world war. They were brought back from the Antarctic in the 1950s by John Cheal, a surveyor with the Falkland Islands Dependencies Survey (which later became the British Antarctic Survey), who had Cheal Point named after him. Both our tins are unopened, so presumably still contain both their cocoa milk and the heating mechanism. It would be interesting to know if they are still self-heating after all these years, but obviously we can’t try this out as they are museum objects. I will just have to try one of the other brands of self-heating tin that are sold today – although this description of the contents as “brown, lumpen, heavily spiced sludge” sounds rather less appealing than a delicious mug of Heinz cocoa milk!

Christina

 

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