Final answer:
Rolling the rod too tightly during a permanent waving procedure can cause hair damage by putting excessive tension on the disulfide bonds, leading to breakage or crimping. Temporary waves involve disrupting weaker hydrogen bonds, which allows the hair to retain a new shape temporarily after drying.
Step-by-step explanation:
When permanent waving hair, rolling the rod too tightly can cause hair damage such as breakage or undesired crimping. This is because permanent waves alter the hair by disrupting and reforming the disulfide bonds within the hair strands, which are primarily responsible for the strength and elasticity of the hair. When hair is rolled too tightly on the rod during a perming process, it can put excessive tension on these bonds, leading to potential damage.
Temporary waves, on the other hand, involve a more mild manipulation of the hair's structure. They rely on disrupting hydrogen bonds, which are weaker than disulfide bonds. When the hair gets wet, water molecules disrupt some of the hydrogen bonds within the keratin strands of the hair. As the hair dries and these bonds reform, the hair can take on a new shape temporarily until it gets wet again.