Why Does Wet Paper Turn See-Through?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why does wet paper turn see-through?

The Big Idea

Dry paper scatters light at every air gap between its fibers. Water or oil fills those gaps and bends light less, so more light slips straight through. The wet patch lets more light pass, and it looks see-through.

Dry Paper

Step one: dry paper. Between the fibers are tiny pockets of air. Light bends and bounces at every edge, so the paper looks white and cloudy.

Add Water or Oil

Step two: add water or oil. The liquid soaks in and replaces the air. Water and oil are much more like the fibers than air is, so light bends less.

Light Slips Through

Step three: light slips through. With less scattering, more light passes straight through the wet spot. That spot looks darker from the front, but clear when held up to light.

A Closer Look

Let's take a closer look! Dry paper scatters light, so it blocks the view. A wet spot scatters much less light. A grease spot on a paper bag turns clear. The clear spot shows best when you hold the paper up to a window.

Quick Facts

Quick facts! Oil soaks into paper and makes it translucent. Some see-through papers are made this way. When the water dries, the air returns and the paper turns white again. Wipe up oil spills right away.

Think Like a Scientist

Now, think like a scientist! Put one small drop of cooking oil on a piece of paper bag or paper towel. Hold it up to a window, but not toward the Sun. What happens to the spot? Does it get lighter or darker?

Outro

Water or oil in the gaps makes paper see-through. Science is amazing! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!