An emulsion system contains an oil phase, an aqueous phase, and an emulsifying agent.
For o/w emulsion systems, the following emulsifying agents
are used:
(i) Water-soluble soap
(ii) Cetyl alcohol
(iii) Glyceryl monostearate
(iv) Combination of emulsifiers: triethanolamine stearate +
cetyl alcohol
(v) Non-ionic emulsifiers: glyceryl monostearate, glyceryl
monooleate, propylene glycol
stearate
For w/o emulsion creams, the following emulsifiers are
used:
(i) Polyvalent ions e.g. magnesium, calcium, and aluminum
are used.
(ii) Combination of emulsifiers: bees wax + divalent calcium
ion
The viscosity of this type of cream prevents the emulsified phase's coalescence and helps stabilize the emulsion.
Example: Cold cream
Procedure:
(i) Water-immiscible components e.g. oils, fats, and waxes
are melted together over a water bath (70°C).
(ii) Aqueous solution of all heat-stable, water-soluble
components is heated (70°C).
(iii) Aqueous solution is slowly added to the melted bases
with continuous stirring until the product cools down and a semi-solid mass is
obtained.
Note: The aqueous phase is heated otherwise, with a high melting
point fats and waxes will immediately solidify with the addition of a cold
aqueous solution.