Cut the paper to a size that will fit the plastic bag.
Draw anything you like – as long as it’s full of color.
Place your drawing inside the bag and seal it. Make sure the bag is stretched and has no “wrinkles”. You can use any clear plastic bag as long as it’s well-stretched (use the duct tape to stretch it).
Use the black permanent marker to trace the outline of your paper drawing on top of the plastic bag. You can draw anything you like, as long as the outline is identical.
Fill the mug with water.
Insert the plastic bag into the water. Put it in and then take it out and watch how the colors of your drawing disappear, and only the black outline remains!
If your plastic bag is too big for the mug, fold the surplus areas back and tape them. Make sure the plastic bag is stretched when you put it in the water.
Can you still see the colors of your drawing? Tilt your head until you find the right angle for the colors to disappear!
What’s the science behind this?
Simply put, the colors disappear because light rays bend (change direction) when they hit the water, a process called refraction.
Every object we see reflects light. Light rays hit it, and the reflected light from the object reaches our eyes. When we inserted the plastic bag into the water, the light did not reach our eyes and the colors of the paper drawing “disappeared.”
That happens because light rays change direction when they pass from air into water.
Once we insert the plastic bag in the water, the light rays must go through two materials before they reach our eyes – the air in the bag and the water. As they pass from one material to the next, the light rays slightly change course and therefore do not reach our eyes. This creates the illusion that the colors have disappeared, although, of course, they are still there on the paper…
So, why hasn’t the black drawing on the plastic bag disappear? Since we drew on the plastic bag, the light rays reflected back only has to pass through one material – the water – and were therefore able to reach our eyes.