How many times can you fold a piece of paper? There’s a myth that you cannot fold it perfectly in half more than eight times, but given a large enough piece of paper, and using powerful hydraulic equipment, you could fold a piece of paper as many times as you wanted.
The Hydraulic Press Channel on YouTube decided to use this exact type of equipment to fold a piece of A3-sized paper seven times, something that is considerably difficult to do using just human hands. After attempting to fold it for the seventh time, however, it appears to cause the paper to explode, transforming the remnants into brittle, fractured pieces.
So why did the paper appear to explode? Well, one possibility is that it wasn’t the paper at all.
For any bit of paper, after the first fold, it doubles in thickness. Another fold, and it quadruples in thickness. By the seventh fold, it would have become 128 times thicker than it was originally. This is known as exponential growth, and explains why a piece of ordinary paper folded 23 times would be a kilometer (0.62 miles) thick. Forty-two folds will stretch out to the Moon, and 103 folds will expand beyond the observable universe.
At the same time, each additional fold is harder to make as it requires rapidly increasing amounts of pressure to squash the increasingly thicker bit of paper. On the seventh fold, the hydraulic press is using incredible pressures in order to achieve its goal. When the fold breaks the piece of paper, the press suddenly juts forwards, creating the explosion noise.
A few years back, the Mythbusters team successfully folded a much larger bit of paper a total of 11 times with the aid of a steamroller – and yet, there was no explosion. This seems to suggest that the hydraulic press is to blame for the explosion noise in the now-viral YouTube video.
However, another possibility is that the "explosion" is down to the crystals of calcium carbonate found within the paper, a common component added during the manufacturing process. The stress put on the seventh fold compressed these rigid crystals to the point of sudden collapse, which led to the catastrophic failure of the paper.