Final answer:
Chemical depilation is the type of hair removal that uses a caustic alkali preparation to break down disulfide bonds in hair, allowing for easy hair removal. It is typically done with a cream or lotion that contains calcium thioglycolate.
Step-by-step explanation:
The type of hair removal that uses a caustic alkali preparation is chemical depilation. Chemical depilatories, such as those in creams and lotions, contain active ingredients like calcium thioglycolate, which work to disintegrate the hair by targeting the disulfide bonds in keratin. These products maintain a high pH level, usually around 12, due to the presence of calcium hydroxide or strontium hydroxide in the formulation. A typical hair removal process using chemical depilatories requires about 10 minutes, after which the area is rinsed, and skin conditioners are applied to neutralize the skin's pH back to normal.