- The pH scale runs from 0 to 14; 7 is neutral
- As pH falls below 7 acidity increases
- Hair has low/medium acidity, it's pH ranges from 4 to 5.5
- As pH rises above 7 alkalinity increases
- Note that a fall in pH from 5 to 4 represents a 10-fold rise in acidity and a fall from 5 to 3 is a 100-fold rise in acidity; the same is true for alkalinity, i.e. pH = 9 is 100 times more alkaline as pH = 7
Hair is not tolerant to extremes of pH, this is what happens to it as pH changes:
What is the pH of healthy natural hair? Why does it matter?
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