Why does paper stay folded but a blanket goes floppy?

Fold a sheet of paper, then open it up. A line stays right where you folded! But a soft blanket on your knees goes all floppy. Why does paper stay folded but a blanket goes floppy?

The answer is hiding in fibers. Fibers are tiny strands, even thinner than a hair. Paper is made of fibers from wood. A cotton blanket is made of fibers from the cotton plant.

To make paper, paper makers mix the fibers with lots of water. They spread them into a thin, flat layer. Then they squeeze out the water and dry the layer. As it dries, the fibers stick together.

In paper, the fibers hold on to each other, like many little hands holding tight. That is why a sheet of paper feels a bit stiff. Its fibers cannot slide around.

When you press a fold into paper, some fibers bend and some let go of each other. They cannot go back the way they were. So the fold stays as a line.

Now think about a soft blanket. Are its fibers stuck together too, just like in paper? Make a guess!

Cloth makers do something different. They twist the fibers into threads. Twisting turns lots of tiny fibers into one long, thin string, like the string on a kite.

Then cloth makers weave the threads, over and under, over and under. The threads cross each other, but they are not stuck together. They can still slide and move a little.

When a blanket lies on your knees, its own weight pulls the edges down toward the floor. The threads slide and bend, so the blanket goes soft and floppy. It hugs your knees instead of keeping a line.

A blanket can get a fold line too, if it stays folded for a long time. But its threads can move, so it bends much more easily than paper.

Fibers and threads. Paper stays folded because its fibers are stuck together, but a blanket goes floppy because its threads can move.

As your blanket settles softly over your knees, now you know why it hugs you so gently.