An emulsifier or emulsifying agent is a compound or substance that acts as a stabilizer for emulsions, preventing liquids that ordinarily don’t mix from separating. An emulsifier keeps immiscible compounds from separating by increasing the kinetic stability of the mixture. Surfactants are one class of emulsifiers, which lower surface tension between liquids or between a solid and liquid. Surfactants keep droplets from getting large enough for components to be able to separate based on density.