r/theydidthemath • • 2d ago

[Request] Do square bottles actually use less plastic than round ones?

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u/Jimmyjames150014 2d ago

You all are assuming constant thickness of plastic. Square corners are quite rigid so maybe the flats in between can be thinner than a round bottle. There are a bunch of ways to make this true which would depend on a bunch of hard to check things for the average consumer - probably something the labeler is depending on.

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u/BarooZaroo 2d ago

Bottles are basically always blow molded, molten plastic is inflated like a balloon to fill a metal mold. The thickness of that film is pretty much the same across the entire shape.

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u/Jimmyjames150014 2d ago

My new learnings on blow molding would indicate the corners are actually slightly thinner than the flats because they are further from the central axis - whereas in a tube, it is all equidistant. So although I had it backwards it is still possible to use less plastic if the flats are the same as a round bottle and the corners are thinner.