The globules of the disperse phase coalesce together and form a separate layer. Redispersion cannot be achieved by shaking and the preparation is no longer an emulsion. Cracking may be caused by the following:

1. Addition of emulsifying agents of the opposite type. Soaps of monovalent metals produce O/W emulsions whereas soaps of divalent metals produce W/O emulsions. Addition of a monovalent soap to a divalent soap emulsion or vice versa leads to cracking. Anionic and cationic emulsifying agents are mutually incompatible. Gums, proteins, gelatin and casein are insoluble in alcohol and if alcohol is added to emulsions prepared with these materials, the emulgent is precipitated and cracking occurs.
2. Decomposition of the emulsifying agent due to microbial action. Emulsions not intended for immediate use should contain a preservative to prevent growth of molds and bacteria, which might over a period of time destroy the emulsifying agent and cause cracking.
3. Addition of common solvent. The addition of a liquid in which both the disperse and continuous phases are soluble forms a one-phase system and destroys the emulsion.
4. Oil turning rancid during storage. The acid formed denatures the emulsifying agent, causing the two phases to separate.
5. Change of storage temperature. The change of extreme storage conditions during the shelf life may lead to the cracking of the emulsion.