Understanding Biphasic Liquid Product Behavior: Separation, Milky Appearance, and Color

Based on your description, the product is likely a biphasic liquid formulation, which contains two layers that don't mix naturally, typically water and oil.

Here's why it behaves this way:

• Separation: Water and oil are immiscible, meaning they do not mix together. When the product sits, these two phases separate into distinct layers due to their different densities.
• Milky appearance when shaken: Shaking the product temporarily disperses tiny droplets of the oil phase into the water phase (or vice versa). This creates a temporary emulsion, and the scattering of light by these droplets makes the liquid appear cloudy or milky.
• Separation after shaking: Unlike stable emulsions (which use emulsifiers to keep phases mixed), biphasic products rely on temporary mixing. Without sufficient emulsifiers, the dispersed droplets will eventually recombine, causing the layers to separate again over time.
• Pink color: The pink color is likely due to a colorant that has been added specifically to the oil phase of the product. This colorant is soluble in oil but not in water, so it only colors the oil layer.

This type of formulation is designed to be shaken before each use to ensure you apply a mixture of both phases.