We’ve all experienced this daily scene at the supermarket: arms full of milk, bread, biscuits and that stubborn packet of detergent that always threatens to escape. The cashier, with his professional smile, holds out “the bag” towards us, this marvel as light as a feather, but he … Durable enough to withstand all the loot without flinching. We grab it by the comfortable handles and, once home, we put it in the recycling bin.
The result is not so innocent: a plastic ghost that will take between 400 and 1,000 years to completely degrade, floating in the oceans and fooling the sea turtles who ingest it into mistaking it for appetizing jellyfish.
But the true story of this inseparable companion of our weekly purchases was born as an ecological hero thanks to chance and ended up becoming the perfect symbol of uncontrolled consumerism.
If you imagine that it came from the mind of an evil genius in a white coat, prepare to be surprised, because its creator just wanted to save the trees.
The chemical accident that changed everything
The adventure began in 1933 in a fairly modest chemical factory in Northwich (England). A chemist named Reginald Gibson experiments with ethylene under high pressure – an unglamorous job focused on producing synthetic gasoline for automobiles. Suddenly, an unexpected chemical reaction occurs that gives rise to polyethylene, a white, flexible plastic that’s incredibly cheap and strong like few others.
The British called polyethylene a “state secret” during World War II because it was used to insulate enemy radars and floating tanks in the English Channel. However, in the post-war 1950s, this material became the new industrial star: waterproof, durable and ridiculously low cost.
In Sweden, the company Celloplast – specializing in cellulose for paper packaging – immediately understood its potential. The development department was headed by Sten Gustaf Thulin (1914-2006), a tall and serious engineer whose mustache resembles that of a contemporary Viking. Thulin scratched his head and thought, “Why don’t we make bags out of this plastic?”
At that time, Swedish supermarkets were consuming entire forests to produce paper bags – up to fourteen million trees a year in Sweden alone. Thulin saw the opportunity: a reusable, affordable alternative that would end mass deforestation. He was not a mad visionary, simply a pragmatic scientist.
It should be noted that Thulin did not invent the plastic bag from scratch; rudimentary prototypes had existed in the United States since the 1950s in the form of manually sealed tubes. Of course, they were expensive, fragile and impractical. What Thulin managed to do was produce them on a large scale.
Now comes the stellar moment, the real accidental eureka. Thulin was experimenting with ultra-thin polyethylene tubes (just 0.025 millimeters thick) with the sole aim of making industrial bags for factories. But one day, a frustrated worker bent a flat tube to test its strength… By drilling the ends, natural handles spontaneously formed.
This wasn’t a flash of divine inspiration, it was an extrusion process, which expels the molten plastic like a gigantic toothpaste, generating a continuous, flexible film. By sealing the base, the upper part is perforated and the iconic “loop handles” (flat, reinforced handle) are created, so that we obtain a one-piece bag, without weak seams or joints, capable of supporting up to twenty kilos of weight.
Thulin patented the method in 1965 in Sweden. Celloplast launched it on the market under the name Eco-Bag: a durable, lightweight bag that can be reused up to thirty times. The success, which could not be less, was immediate. Swedish supermarkets adopted it within weeks and offered it free to customers, who reused it as a makeshift backpack. It is said that Thulin always carried a folded bag in his pocket.
Was it pure coincidence? To a large extent yes, but seasoned with a brilliant mind. As in any good story worthy of the name, there was no shortage of other candidates to claim the invention. Among them, Stéphane Branly, who created bags with drawstring handles, but made from fragile paper, or American inventors who patented packaging tubes, which required several parts and were also very expensive.
Thulin triumphed thanks to its revolutionary simplicity: an extruder, a joint at the base and a perforator at the top capable of producing a thousand bags per minute at a cost of only 0.01 cents per unit. A real revolution.
From savior of trees to villain of the oceans
What Thulin designed to last for centuries became a massive disposable product precisely because of its immense success. Bags with handles were cheap (barely a pfennig in the 70s) and hygienic. Supermarkets started handing them out like they were candy. In 1977, in the United States alone, sixty-five billion were already produced per year.
Unfortunately, luck turned against the invention, its durability turning it into eternal trash. Plastic bags take between 400 and 1,000 years to degrade, releasing microplastics which end up in the bodies of fish… and in our food chain. The irony is crucial: Thulin stopped the massive felling of trees – saving millions of people – but created the worst marine plague on the planet.
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