Can You Draw on Plastic Foil

Make Your Drawings Float!

An animating science project from Science Buddies

Draw away! Use a little chemistry to make your own moving sketches.  Credit: George Retseck

Key concepts
Chemistry
Polymer
Solvents
Material science

Introduction
Have you ever wished your drawings would come alive and the stick figures or objects on your paper could move around? It's not as impossible as it sounds! In this activity you will make your drawing move around by letting it float on water. What makes this possible is the interesting chemistry of dry-erase markers. These markers are usually used to write on whiteboards or glass surfaces and can easily be erased. It turns out they are also perfect for doing science!

Background
You might have a whiteboard in your school classroom. To draw on this surface, your teacher probably uses a whiteboard pen or dry-erase marker. The writing from these markers can easily be erased from the whiteboard without leaving any marks.

This is possible because dry-erase markers contain special ingredients. They include a solvent, which is usually some kind of alcohol. This is used to dissolve the color pigments that determine the marker's color. In addition, a resin or polymer is added, which is the key to making the ink erasable. In a dry-erase marker the resin is an oily silicone polymer, which acts as a "release agent." This makes the ink of the marker very slippery and prevents it from sticking to the whiteboard's surface. This is why the ink can easily be wiped off from a very smooth nonporous surface such as a whiteboard or glass.

You might know dry-erase markers can stain other surfaces such as clothes permanently. This is because fabric doesn't have a smooth surface, so the ink can soak into its pores—staining them forever! In real permanent markers the resin used is an acrylic polymer that functions as a "binding agent" and makes the ink stick to the surface. Only the type of polymer differentiates a permanent marker from an erasable marker. Find out how this difference affects how your drawings float in in this activity!

Materials

• Two shallow trays or plates with smooth surfaces that you have permission to draw on with markers
• Dry-erase markers (different colors)
• Permanent marker
• Cup
• Water
• Rubbing alcohol
• Paper towels

Preparation

• Find a work area that can tolerate water spills.
• Fill your cup with room-temperature water and set it next to your trays or plates.

Procedure

• Choose one color of your dry-erase markers and make a drawing on your first plate such as a stick figure, a heart or word. Does it look like the ink is sticking to the surface of your plate?
• Let it dry for a couple of seconds and then use a dry finger to wipe across your drawing. Does your finger wipe off the drawing, or can you still see it afterward?
• If the drawing came off, make a new drawing. Otherwise, keep the old one. Then pour just enough water onto your plate to cover the drawing. Wait and observe. If nothing happens, shake the plate a little bit. What happens to the ink after a while? Does your drawing begin to float and come to life?
• Next use a permanent marker to make a drawing on the second plate. Do you see a difference from how the dry-erase marker looked on the surface?
• Let it dry for a couple of seconds and use a dry finger to wipe across your drawing. Does your drawing disappear once you wipe it with your finger? Can you explain why or why not?
• If the drawing came off, make a new drawing. Otherwise keep the old one. Then pour some water on your plate to cover the drawing. Wait and observe. What happens to the drawing this time? Does it float? How are your results different from the previous ones?
• Extra: Make drawings with different colors of dry-erase marker. Do all of them behave the same way or are they different? Which color floats best?
• Extra: What happens if you pour rubbing alcohol on top of your drawing instead of water? Does your drawing still float? Do dry-erase and permanent markers give you the same result? Why or why not?
• Extra: Can you erase your floating drawing? Try to pick up your drawing from the water's surface with your fingers. What happens to it when you pull it out of the water? What do you think the material you now have in your hand is made of?

Observations and results
Did you get your drawings to float? You should have—but only when using the dry-erase marker. When you make your drawing on the surface of a smooth plate or tray the solvent, or alcohol, that dissolves the ink ingredients will evaporate. This leaves the color pigment and polymer behind on the surface. With the permanent and dry-erase markers, it actually looks like the color is sticking. When you wipe across your drawing with your finger, however, only the drawing that you made with the dry-erase marker will disappear. This is because the oily silicone polymer in the dry-erase marker prevents it from sticking whereas the acrylic polymer resin in the permanent marker makes it stick to the surface.

The fun starts when you pour water on your drawing. You should have observed your dry-erase marker drawing magically detached from the plate and rose to the water's surface. There, it could float and move as if it were alive! The permanent marker drawing should have remained stuck to the plate. This difference is due to the special polymer in the dry-erase marker ink—because this ingredient prevents the ink from attaching to the plate, and the water can slip underneath. And because the ink is lighter than water it can float. When you poured rubbing alcohol on your drawings, however, you should have seen them both slowly dissolve. This is because alcohol is used as the solvent in both markers.

Cleanup
Remove all remaining drawings from your plates by rubbing them with a paper towel soaked in rubbing alcohol. Then rinse them with warm water and soap before reusing them.

More to explore
Make Your Own Markers, from Science Buddies
Chromatography: Be a Color Detective, from Scientific American
Soluble Science: Making Tie-Dye T-Shirts with Permanent Markers, from Scientific American
Science Activity for All Ages!, from Science Buddies

This activity brought to you in partnership with Science Buddies

Can You Draw on Plastic Foil

Source: https://www.scientificamerican.com/article/make-your-drawings-float/

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