An emulsifier is a surface-active agent which lowers the surface tension between non mixable liquids. The lower surface tension allows the two liquids to share a larger contact surface. Typically one liquid forms droplets (and is called the discontinious phase) in the other liquid (the continious phase).

In water/oil systems the type of emulsifier can influence whether the oil or the water will be the discontinious phase. SCATTICS emulsifiers being more hydrophillic (higher HLB value) typically form Oil in Water (O/W) emulsions. MONICS emulsifiers predominantly being lipophillic (lower HLB value) enhance a Water in Oil (W/O) emulsion.