An activity you can use in the classroom
Crime labs use a process called chromatography to separate ink into the individual chemicals that are used to make it. Each pen manufacturer uses a unique blend of chemicals, and each of these chemicals has its own distinct color. In this activity, you'll use chromatography to analyze ink mixtures from a variety of pens.
- 4 filter strips, each about 1 inch x 4 inches (2 cm x 10 cm),
cut from coffee filters
- 4 clear plastic cups
- 4 Popsicle sticks
- 4 ink pens, each made by a different manufacturer
- scissors and tape
- water
- Attach each filter strip to a Popsicle stick so that it hangs in the center of the plastic cup. Note: Your strips should just touch the bottom of the cup.
- Using a different pen for each strip, draw a .4-inch (1-cm) dot that's 2 inches (5 cm) from the bottom of the strip.
- Pour approximately 1-1/4 inches (3 cm) of water in each cup.
- Place the first strip into the water, making sure that the ink dot is above the water line, and rest the Popsicle stick on the rim of the cup.
- Watch as the water rises up the filter paper - this process is called capillary action — and record your observations on the attached worksheet.
- Remove the filter strip, setting it aside to dry.
- Using a clean cup of water each time, repeat steps 4-6 using the remaining three strips of paper.
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