Granted, I have been wearing a beany hat all day and it is in plaits but even when it's loose my hair does take a long time to dry.
The key driver of the rate at which hair dries is its porosity.
Porosity refers to how easily water and other chemicals can diffuse into and out of hair. If the outer layer of the hair fibre, the cuticle, is very tightly bound and lies very flat the hair is not very porous. This type of hair is quite resistant to the entry and exit of chemicals including water.
If the cuticle layer of hair has been damaged, it's weak and much more porous. Porous hair dries much more quickly than non-porous hair.
Porous hair once moisturised loses that moisture much more quickly than hair that is not porous.
- When it's hot hair dries faster;
- When the heating inside a home or other building is high, hair dries faster;
- Setting lotions help hair to dry more rapidly;
- The use of a blow drier obviously accelerates the rate at which hair dries and the more intense the heat, the faster hair dries.
According to The Science of Black Hair, an intensely hot blow dry for a short period of time (10 - 20 minutes) is far more damaging than much milder heat application for a longer period of time, e.g. sitting under a hooded dryer for 45 minutes.
Keep these factors in mind when you want your to dry fast!