This paper chromatography experiment for students uses washable marker ink, filter paper and water to show that a colour can contain several dyes. It is designed as a short classroom investigation: learners make a prediction, keep the solvent below the pencil baseline, observe how colours travel and compare results. The method avoids alcohol and other laboratory solvents. Use teacher supervision, check the marker label and follow your school’s usual practical safety rules.
Learning goals
- Describe chromatography as a way to separate parts of a mixture.
- Identify the paper as the stationary phase and water as the moving solvent.
- Record a result and explain why different dyes can travel different distances.
- Make a fair comparison by changing one factor at a time.
Materials and preparation
For each group, prepare a strip of white coffee filter paper or classroom filter paper, a washable water-based marker, a clear cup or small beaker, water, a pencil, a ruler and a clip or pencil to suspend the paper. Scissors should be handled according to school rules. Before class, test one black marker and one coloured marker because some washable inks separate more clearly than others. Use a pencil for the baseline; pen ink may dissolve and travel with the solvent.
Set up the chromatogram
- Cut a strip that can hang inside the cup without touching its sides.
- Draw a light pencil line about two centimetres from the bottom.
- Place a small, concentrated marker dot at the centre of the line and let it dry.
- Add a shallow layer of water to the cup, keeping the surface below the pencil line.
- Clip or wrap the paper at the top and suspend it so only its lower edge touches the water.
- Watch the solvent rise. Remove the strip before the wet front reaches the top, then leave it to dry.
Ask learners to predict and observe
Before adding water, ask students whether the marker dot will stay one colour or separate. Have them sketch the starting point and write down the marker colour. During the run, record when the first colour begins to spread, which bands appear, and whether one pigment travels farther than another. Ask students to keep their hands off the paper while it is wet. A simple table can include sample name, number of visible bands, farthest colour, solvent-front distance and one observation.
Explain what the class sees
Water moves through the paper fibres. Some dye components dissolve readily in the water and travel with it; others interact more with the paper or move at a different rate. The mixture can therefore spread into visible bands. The paper is commonly called the stationary phase and the water the mobile phase. The experiment demonstrates separation, but colour alone does not identify a chemical. Two inks may look alike and still contain different mixtures, while different markers may produce similar-looking bands.
Make it a fair investigation
Once students understand the basic setup, invite them to compare two washable markers using identical paper strips, dot sizes, water depth, cup shape and observation time. Change only the marker brand or colour. Ask each group to repeat the test and compare patterns. For a more structured extension, measure the distance from the pencil baseline to the centre of a visible band and to the solvent front. Students can discuss why small spots, a level baseline and stopping the run at a similar point make comparisons more useful.
Troubleshooting and safety
If the spot drops into the water, the solvent level started above the baseline; reset the strip with less water. If nothing moves, check that the paper touches the water and try a different washable marker. If the spot spreads into a blur, let it dry and apply a smaller dot. Keep the activity to water-based inks and water. Do not substitute rubbing alcohol, acetone or other solvents in a classroom version without an appropriate risk assessment, trained supervision and school approval. Do not taste markers or experimental materials, and wash hands after the activity.
Discussion questions and exit ticket
- What moved through the paper: the paper, the water, or the dye?
- Why must the water begin below the pencil line?
- What evidence suggests that one marker colour contained more than one dye?
- Which variable did your group change, and which ones did it keep the same?
- What can this test show, and what can it not prove about an unknown ink?
Ask each learner to finish: “The colour separated because…”, “One result I observed was…”, and “A fair comparison needs…”. Accept an observation that differs from another group when the setup or marker differs; ask students to cite what they saw rather than copy a predicted result.
Teacher note and sources
The Royal Society of Chemistry describes classroom chromatography as an opportunity to develop practical skill, compare observations and improve the investigation. Its learning material also notes that paper chromatography may give limited separation, so avoid promising textbook-perfect bands. This simplified water-only activity is suitable for a supervised lesson, not a chemical identification test. Adapt the age level, accessibility supports and safety review to your classroom. [RSC classroom practical](https://edu.rsc.org/primary-science/kitchen-roll-chromatography/4012057.article) · [RSC teaching guidance](https://edu.rsc.org/cpd/practical-chromatography-teaching-practical-science/2500327.article) · [Imperial College STEM activity](https://www.imperial.ac.uk/media/imperial-college/be-inspired/student-recruitment-and-outreach/public/stem-in-action/Chromatography-Instructions.pdf).
