When you squirt toothpaste how has it got neat coloured stripes on it? Surely in the tube it would all get mushed up?
In: 3
The original invention by Marrafino ([https://patents.google.com/patent/US2789731](https://patents.google.com/patent/US2789731)) is shown in this German ELI5 style video: [https://youtu.be/Pius1MtUIrY](https://youtu.be/Pius1MtUIrY) – In short: there is an short inner plastic cylinder with fine holes behind the nozzle of the tube. In the factory you fill part of the tube around this cylinder with colored tooth paste and the rest with white one. If you press on the tube you force a thin stream of colored tooth paste through the holes onto the white center stream.
There are also more modern approaches that allow for multiple colors by adding additional reservoirs (e.g. [https://patents.google.com/patent/US4969767](https://patents.google.com/patent/US4969767)) and there seems also a system to fill the tube with stripes already present as shown in [https://beachpackagingdesign.com/boxvox/cutting-open-toothpaste-tubes](https://beachpackagingdesign.com/boxvox/cutting-open-toothpaste-tubes) – which requires some rheological trickery prevent the different colors from mixing.
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