Why does soapy water sometimes look milky

Why does soapy water sometimes look milky  

Soapy water often looks milky. This milky appearance indicates that a colloid has formed, with one phase suspended in another. But soapy water introduces another complexity whereas water containing a lot of soap does indeed have a cloudy aspect, dilute solutions of soap are not cloudy, but clear. We see this behaviour when washing our face in the sink (yielding a concentrated and, therefore, milky soap solution) or washing in a larger volume of water, such as a bath, when the water can remain clear. Whether or not a soap solution forms colloid depends on its concentration. 

The word micelle comes from the diminutive of the Latin word mica, meaning crumb.  

We are dealing here with a new type of colloid the micelle. 

Although the micelle particle is an aggregate, it behaves like a liquid indeed, it is often convenient to regard these micelle aggregates as a separate phase. For this reason, we usually class micelles as a liquid-in-liquid colloid. 

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