How does the pH scale measure the acidity of a product?

The pH scale is a measurement tool that indicates the acidity or alkalinity of a solution, ranging from 0 to 14. In this scale, a value of 0 corresponds to the most acidic substances, while a value of 14 indicates the most alkaline or basic substances. A neutral pH value, such as that found in pure water, is represented at 7.

This means that when a product has a pH value lower than 7, it is considered acidic, and as the pH value increases beyond 7, it becomes more alkaline. Understanding this scale is crucial in cosmetology and barbering because the pH level of products can affect their performance and compatibility with different hair and skin types. For instance, hair has a natural pH of around 4.5 to 5.5, making it slightly acidic, which helps maintain the health and integrity of hair.

The other options misrepresent the scale or its measurements, leading to confusion about how acidity and alkalinity are quantified. For example, indicating 0 as most alkaline or using different numeric ranges undermines the foundational understanding of the pH scale in evaluating cosmetic products.