Coffee Filter Chromatography
Here’s a great activity to see chromatography in action.
* A note on markers: We found that Mr. Sketch markers worked better for this than Crayola markers and Target brand markers. Be aware that your results will vary depending on the markers that you use.
- Draw with a marker on the coffee filter. We liked drawing just around the base.
- Pinch the bottom of the coffee filter or pull it into a point.
- Place just the bottom of the filter in water.
- Watch the water draw the colors apart!
We found that not only did different marker brands give you different results, but that the different colors are made up with varying levels of complexity. Our favorites were brown and black. These were made up of many colors. Some colors like yellow and light blue didn’t show any other colors present.
What is Chromatography?
You can see chromatography for yourself with coffee filters that have been drawn on with markers. When the porous (having small spaces or holes) coffee filter is placed in water, capillary action draws the water up. Capillary action is the ability for a liquid to flow in narrow spaces without the help of gravity. The filter has tiny empty spaces that the water fills up. Surface tension helps the liquid keep moving along.
As this liquid moves along, the colors that make up the marker color separate because that travel at different speeds. Chromatography is when a mixture passes through a solution or gas and the mixture’s parts move at different rates.
Application in the Real World
Chromatography is used in forensic science (identifying samples from a crime scene), pollution monitoring (identifying things in air and water), and studying other complex mixtures (like perfume, food, pharmaceuticals, and chemicals).
Let’s get crafty!
Now what are you going to do with all of your wonderfully colorful filters? We used ours to make flowers, butterflies, and bows!