Heat damage

Blow drying causes a “flash drying” effect that not only removes the
surface moisture but also removes water that is bound to the hair,
which is called water of hydration. The effect of this flash drying is
that the cuticles become dried, rigid and brittle. When the hair
flexes, the pressure causes the cuticles to crack. One study (see
Reference 1 below) showed cracks occurring not only on the surface
layer of cuticles, but actually two and three cuticle layers deep.
Combing hair with this degree of cuticle cracking causes significant
breakage.
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Composite Doors | Composite Front Doors

thanks for the information....