Video Tutorial: chromatography
Black ink is black ink, right? Maybe not! Even though the ink from different pens looks the same, it might actually be made of many different dyes. You can separate the dyes in the ink from different pens to make different patterns. Did you know that inks and markers are often combinations of several colored dyes? We can separate these combinations of colors or pigments through a process called chromatography.
Here’s the really cool science behind chromatography…When the paper towel is dipped in water, some of the water sticks to the paper towel and gets it wet. There’s a force between the water molecules and the molecules in the paper towel. That’s called adhesion. The water also sticks to itself. That’s called cohesion. Both of these sticky forces – adhesion and cohesion – cause the water to travel up the paper towel, moving against gravity. When the water reaches the ink, it dissolves some of the dyes in the ink, and the dyes travel up the paper towel with the water. That’s how you can see all the different colors that make up the ink.
1. Draw a squiggly line across a strip of paper towel with one of your black pens or markers.
2. Using a dropper, slowly drop drips of water onto the line.
3. Observe what happens and record your results.
4. Let your paper towel dry. Now observe your squiggly line. Compare the results to what it looked like immediately after it became wet.
Try it out with different types of pens. Does a scented marker make a different pattern than a non-scented marker? What happens if you use a dry erase marker or a sharpie? What about a gel pen or ball point pen? Explore and have fun!
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