When machining with water-soluble coolants, maintaining coolant stability is essential to produce quality parts and surface finish. Therefore, it is important to mix the coolant properly.
Water-soluble coolants consist of both an oil phase (nonpolar) and a water phase (polar). These phases are extremely dissimilar, so they tend to separate from one another. Hence, emulsifiers are an important component in the coolant concentrate. Emulsifiers are molecules that consist of both polar and nonpolar sides, which help bring the two phases together.