A shampoo with a pH of _____ closely matches the ideal pH of hair.

The ideal pH for hair typically ranges around 4.5 to 5.5, which helps maintain the hair's health and integrity. A shampoo with a pH of 6 is relatively close to this optimal range, being slightly alkaline but still within a reasonable limit that won't adversely affect the hair.

Using a shampoo that is too alkaline (such as those with a pH of 7 or higher) can lead to cuticle damage, making hair more porous and prone to frizz and breakage. Conversely, shampoos that are too acidic (like those with a pH of 4) may not effectively cleanse the hair and could make it more brittle due to their stronger acid effect. Thus, a shampoo with a pH of 6 strikes a good balance, cleansing effectively while also respecting the natural acidity of hair and scalp.