July 29, 2020

Why your updo leaves a dent in your hair

Have you ever taken your hair down from a ponytail and noticed a line right where your hair tie was? Marring your hair with an indentation? That’s not an accident. It’s actually due to the molecular structure of your hair.

Let’s start at the beginning: the basic building blocks of hair. Your hair is composed of keratin, which is a fibrous protein. There are three kinds of bonds that hold together the proteins in your hair: disulfide bonds, salt bonds and hydrogen bonds. Disulfide bonds and salt bonds are the stronger, more permanent bonds in your hair. Hydrogen bonds, however, are weaker. Hydrogen bonds can be broken two ways: with 1) water and 2) heat.


So when your hair gets wet, the hydrogen bonds are broken, and that means your hair can be reshaped. When it dries, it can take on a new form. This is the secret behind rag curls and ponytail dents. So if you hop in the ocean, emerge and put your hair in a braid and then take it down hours later, the waves are preserved by the new bond structure of your hair. And the only way to get rid of it is to break and reform the hydrogen bonds into a new shape. 


And now I’m going to blow your mind: this is also the reason why humidity can change your hairstyle. Humidity is essentially water suspended in the air, and that water can be absorbed into the hair shaft, altering your style (and sometimes introducing frizz).


I mentioned that heat can also break hydrogen bonds. This is why getting a blow-out straightens hair. The heat of the blow dryer combined with a round brush reshapes the hair to match the curve of the brush. The same result can be obtained by the high heat from curling irons and straighteners.


Maybe it’s just me, but it feels a little crazy that the next time I hop in the shower I’ll know I’m breaking bonds in my hair.

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Image courtesy of:

I sought out this information and was not compensated monetarily or otherwise for this post.

1 comment:

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