If hair does not hold a heat style, it is characterized by what type of porosity?

When hair does not hold a heat style, it is typically characterized by low porosity. Low porosity hair has tightly closed cuticles, which makes it difficult for moisture and products to penetrate the hair shaft. This means that heat styling products may not effectively adhere to the hair, resulting in styles that do not last long.

Low porosity hair often feels smooth and may be resistant to moisture and product absorption. Since heat styling often requires the hair to be somewhat receptive to the products applied to it, low porosity hair may struggle to maintain the desired style because the heat does not create a lasting bond with the hair.

In contrast, high porosity hair, which has gaps and holes in the cuticle layer, typically can hold styles better but may become frizzy or lose moisture quickly. Normal and medium porosity hair falls in between these two extremes, generally having a better ability to hold styles due to a balanced structure in the cuticle.