The classic chromatography experiment is always surprising! Did you know you can separate black into different colors? Read on to see how!
Chromatography is the process of separating mixtures. In this project you will separate the color black into other colors. As the coffee filter absorbs water through capillary action, the black ink moves through the filter and is separated by the water into other colors. You should see blue, green and even red as the water separates the ink.
The Classic Chromatography Experiment
- Black washable marker
- Coffee Filters
- Paper Towels
We have two methods for conducting this experiment. One uses coffee filters and one uses paper towels. You may try either or both!
Instructions for Coffee Filter Experiment
Time needed: 15 minutes.
- Fold the coffee filter
Fold a coffee filter in half. Fold in half two more times until you have a triangular shape.
- Color the filter tip
Color the tip of the coffee filter with washable black marker. Get a good coat of ink on the filter.
- Place the filter in water
Add a small amount of water to a plastic cup. Place the black tip of the coffee filter in the cup.
- Wait and observe
Come back to the filter after 15 minutes and see what happens to the ink.
Instructions for Paper Towel Experiment
- Cut paper towel Cut your paper towel into strips
- Color the paper towel Color the center of each strip with black marker.
- Place in water Place the paper towel in a cup with a small amount of water at the bottom. Place the colored center in the water and allow the ends to hang over the side of the cup.
- Watch and observe The ink will begin flowing up the paper towel via capillary action and the pigments will start separating.
- Remove and let dry After a few minutes, remove the paper towel strip from the cup and let dry on a piece of paper.
- Try this with other colors. Does it work as well? What colors can you separate? Which don’t work as well? Keep a chart of how well each color works.
- What happens when you use a permanent marker? Add a few drops of rubbing alcohol over a permanent marker drawing and see what happens.
- Turn these into paper flowers! Add a pipe cleaner stem and wrap around the pointed end of the “flower.”
Chromatography is the process by which scientists separate mixtures by letting them slowly move past each other. In the process of chromatography a mixture in one state of matter moves over the surface of something in another state of matter. In this experiment the water (a liquid) carries the pigment through and over the surface of towel (a solid) and in the process it separates the individual pigment colors. Here is a more in-depth explanation of chromatography.
Capillary action is ability of liquid to flow against gravity through other materials. In this project water and ink moves through the fibers of the paper towel or coffee filter until all the fibers are fully saturated (or until you remove it from the liquid). If you allow the towel or filter to sit in the water for a long period of time eventually all the ink will move to the ends of the filter or towel.
This project is included in our Classic Science Activity Cards here. If you enjoyed it check out the cards for 9 more ideas!