Time travel back to the future with a black shuttle pot popcorn machine

To people born in China before the 1980's, "popcorn" made from microwaves and electronic poppers were just cracked corn kernels, not popcorn. Only kernels that were popped out of old-styled, hand-operated popcorn machines were considered real popcorn.

These old-style, hand-operated popcorn machines were called "Black shuttle pots" and they were responsible for providing popcorn with sweet tastes and memories. Children would gather around the machine and chat together, waiting excitingly for the final "BANG" announcing that the popcorn was finished and basking in the exquisite aroma of popcorn that would waft through the air.

Today, fewer and fewer "Black shuttle pots" can be seen on the street. Some of the main reasons for the abdication of the old-style popcorn machine are  the invention of the electronic popcorn machine, and the lack of craftsmen who know how to operate the old-style popcorn machine skillfully and safely.

If you understood the scientific principles behind the black shuttle pot, you would be filled with regret about being deprived of this tradition and legacy leftover from the last generation.

The principle of a Black shuttle pot is very simple. The device is made up of an
elliptical metal pot with a pressure gauge at the top called the pressure vessel and a connecting rubber sack to hold the popcorn and prevent it from spreading. You put the corn kernels in the barrel and seal them with a cover to ensure it is airtight. There is a pressure gauge on the cover which detects the pressure inside. Then, you heat the popcorn bucket on the fire, ignite and rotate the pressure vessel, and monitor the pressure gauge at the same time.

In the process of continuous heating, the temperature in the pot rises, and the pressure also increases. When the temperature rises to a certain point, the corn kernels will gradually become soft and the water in the corn kernels will vaporize. At this time, the pressure inside and outside the corn kernels should be balanced, so the kernels will not explode in the pot.

When the pressure in the pot rises to 4-5 pascals (measurement for pressure), the top cover of the popcorn pot is ready to be opened. This sudden exposure makes the air in the pot expand rapidly and the pressure decrease quickly, which increases the pressure difference inside and outside the corn kernels, resulting in the rapid expansion of high-pressure steam in the
kernels. The kernels burst instantaneously, which then becomes delicious popcorn.

Dangerous? Not at all. "Myth Busters", an American TV show on the Discovery Channel, shot an episode which tested if this old-styled popcorn machine from China would cause an explosion. They all anticipated it would act as a bomb and if operated incorrectly. It did not explode as they expected it to.

Cool? Absolutely! Do not doubt that an engineering miracle was invented a hundred years ago. According to the 1893 Chicago World Expo Chicago, a British man called Charles Cretors showcased the "Kingery's Steam Power Peanut Roasters" which was considered a rudimentary popcorn machine. Isn't it like time travel back to the future?

Ren Cihan is a G11 student at the Experimental High School Attached to Beijing Normal University.

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