Your friend just got a keratin smoothing treatment, and her hair is pin straight even after showering. So, at that moment, you decide you want to get a keratin treatment done as well, thinking that you’ll get the same results.

On the day of the appointment, you show your hairstylist the picture of your friend’s hair and say: This is exactly what I want! Your hairstylist looks at your hair and tells you that although your friend’s hair became pin straight after the treatment, she can’t promise the same results. 

You wonder: Why is it that the same treatment yields different results?