* Permanent hair dyes: These are generally alkaline, with a pH typically ranging from 9 to 11. The high pH is necessary to open the hair cuticle, allowing the dye to penetrate the hair shaft and react with the hair's natural pigment.
* Demi-permanent hair dyes: These are less alkaline than permanent dyes, usually with a pH between 7 and 9. They deposit color onto the hair but don't lift as much natural pigment as permanent dyes.
* Semi-permanent hair dyes: These are generally acidic to neutral, often having a pH around 4.5 to 7. They deposit color on the surface of the hair and don't penetrate the cuticle as deeply.
* Bleach: Bleach is also highly alkaline, with a pH similar to permanent hair dyes (9-11). This is necessary to effectively lighten the hair.
It's important to note that the exact pH can vary between different brands and formulations. You can often find pH information on the product packaging or the manufacturer's website.