As a child, the multi-colored toothpaste that we squeeze out of the tube is perceived almost like magic. And adults are often tormented by the question: how do manufacturers manage to pack paste of different colors in such a way that the layers do not mix?
Myths
Tricolor paste is a familiar thing since childhood. However, the process of making such a paste seems so mysterious and incomprehensible that many legends and myths have arisen about this. For example, many believe that the tube has soft baffles separating the layers and mixing takes place at the neck of the tube. These baffles, allegedly, not only allow you to pour paste of different colors into the tube, but also prevent mixing when pressing on the tube.
Another version says that the paste in the tube is white, but there are tiny bubbles of paint in the neck that open when you squeeze out the paste and paint it in different colors. Another explanation: different layers of the paste contain different chemical elements (for example, phosphorus), which turn into different colors upon contact with oxygen. True, if you think about it, the latest version explains nothing: neither why layers with different chemical properties do not mix with each other in a tube, nor how they get there.
Debunking these myths is simple: it is enough, for example, to freeze a tube of colored paste and cut it open. You will make sure that the layers of the paste are initially painted in different colors, and they are not separated by any partitions.
Reality
In fact, there is no magic or special secrets in making multi-colored pasta. The multi-colored paste is made using the same apparatus as the one-color one. However, the paste does not enter the tube through one dispenser, as usual, but through several - for each color it is different. Each layer of the paste is made separately and can have different chemical properties: for example, one layer fights off pathogenic bacteria, the second freshens breath, the third clears plaque and keeps the teeth white.
In order for the layers not to mix with each other, they must have a certain consistency: if the density of the paste is insufficient, then in accordance with the laws of physics and chemistry, mutual penetration of colors will occur. The finished components of the paste from different containers through separate dispensers are poured into the tube in parallel layers. A special machine squeezes thick and viscous "sausage" paste through the back of the tube. After filling the tube with paste, the back walls of the tube are connected and sealed.
As a rule, when squeezing out the paste, you squeeze the tube evenly in the central part, as a result of which approximately the same pressure is applied to all layers of the paste. Since the density of different layers of the paste is also approximately the same, and they are poured evenly, an acceleration of approximately equal force is transmitted to all layers. As a result, uniformly colored stripes of multi-colored paste appear from the tube.
