If you’ve been on this planet for more than 10 years, you should have noticed by now that oil and water don’t mix (if you haven’t, please go to your kitchen and pour some oil into a glass of water IMMEDIATELY. Then come back and read the rest!).
The reason for this is that there are two basic categories of chemical – polar and non-polar. Polar things mix together, and non-polar things mix together. Water, salt, sugar and vinegar are examples of things that are polar, while oils, fats, butters, grease and turpentine are non-polar. Some things, such as acetone, can mix with both categories.
Soapy cleansers can also mix with both polar and non-polar substances – they’re a special kind of chemical called surfactants. These have a polar “head” (purple circle) and a non-polar “tail” (zig zag).
Sodium lauryl sulfate is an example:
This makes them special because they can help the oil come off into water, and we use them all the time – dishwashing detergent helps cooking oil come off, shampoo cleans grease from hair. The soap surrounds the oil in little drops called micelles, with the non-polar bit sticking in (with the oil) and the polar part sticking out (with the water), so everything’s happy hanging out together.
This is what happens as you wash your face using the OCM (click for larger):