Straight wet curly hairs...

People with curly hairs must have noticed that their hairs become straight when the hair is wet and this is due to presence of protein keratin which absorbs water. And gravity acts on the hair so the curls get straightened just like when you stretch a spring but when the water loose its moisture it retains it usual curliness.

In fact, the rate of change in the length of hair strands is so dependable that they can actually be used as the basis for a hygrometer, a device that measures the humidity level in the air. Hygrometer uses horse hair strands.

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