Aree Witoelar Toothpastes often use two or more colors to form stripes. While not providing hygienic benefits, it has interesting appearance for the customer . Here we investigate and discover two different mechanisms to achieve consistency of the color ratios. Two sample tubes of toothpaste are chosen randomly from the market, and labeled as A and P (Figure 1). The samples are cut across the toothpaste compartment (Figure 2).
(not shown). The outlet must have two inputs for each color, one at the body and another at the head (Figure 4 bottom).
Figure 3. Cross section of tubes A (top) and P (bottom) at the toothpaste compartment.
Figure 4. Tube outlets of A (left) and P (right). Figure 1. Toothpaste with multicolored stripes, labeled as A (top) and P (bottom). The mechanism of A is simpler and may promise lower tube production costs. However, it is worth noting that the laminar flow it requires depends on the characteristics of the paste and width of the opening. Otherwise, a turbulent flow can occur (Figure 5).
Figure 2. Method of experiment. The incisions reveal two different mechanisms of toothpaste consistency and outlets. Sample A shows multicolored paste in one compartment (Figure 3 top), which flows parallel to each other. The outlet of the tube is a simple opening (Figure 4 top). Sample P reveals non-mixing paste, with one color at the body (Figure 3 bottom) and the second at the head of the compartment
Figure 5. The toothpaste A has laminar flow on the left, but turbulent flow on the right due to larger opening. Reference 1. Striped toothpaste http://en.wikipedia.org/ wiki/Toothpaste#Striped_toothpaste