To mix two immiscible substances, you first need to break down one of them into millions of tiny droplets. You can then suspend these droplets in the other substance by blending both with an industrial blender. The droplets become known as the dispersed phase, while the other liquid becomes the continuous phase.

Emulsions can be  either oil-in-water (O/W) and water-in-oil (W/O). To form oil-in-water emulsions, the dispersed phase must be oil and the continuous phase, water. For water-in-oil emulsions, the phases are the opposite. However, these substances will not stay mixed for long on their own, and this is where the use of emulsifiers becomes necessary. Emulsifying equipment such as shear mixers and high-speed agitators are essential to prevent separation.

For starters, packaging laws in several countries oblige you to clearly state whether products are suitable for internal or external use on their labels. You should also use wide-mouthed bottles for viscous emulsions and state clearly on the label that the product should be shaken thoroughly before use. Finally, low temperatures can contribute to the demulsification of emulsions, so you should avoid refrigerating them.