Marker chromatography with a coffee filter
Recommended age: 8+. Adult supervision required! With a glass of water and a coffee filter we separate the colours that make up marker ink — revealing how many colours 'black' is really made of.
Chemicals
- 100 ml tap water
- 4 pc round coffee filter or blotting paper (white works best) — white works best
- 4 pc water-based marker (dark colours — black, brown, dark green — are the most spectacular; alcohol-based markers do not work with water) — dark colours — black, brown, dark green — are the most spectacular; alcohol-based markers do not work with water
Procedure
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Cover the table with newspaper and put on your goggles. Do not put markers in your mouth, and use the scissors with the adult's help.
Safety! -
Cut the coffee filter into strips about 3 cm wide and a palm's length long — one for each marker you test.
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Draw a fat dot about 2 cm from the bottom of the strip with the first marker. Label the top of the strip in pencil — pencil does not dissolve, so it will not interfere.
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Pour a finger's depth of water into the glass so that the water level stays BELOW the dot when the strip dips in.
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Clip the top of the strip with a clothes peg to the skewer laid across the glass, so the bottom of the strip just touches the water.
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Watch for 10-15 minutes as the water creeps upwards and carries the colours with it — the dot splits into coloured bands!
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You can race several markers in several glasses at once. Black is the most exciting: depending on the brand it can split into blue, purple, even orange bands.
Technique -
When the water reaches the top of the strip, take the strips out and lay them on the newspaper to dry.
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Compare the dried chromatograms: how many pigments were hiding in each marker? Write down your discoveries.
Apparatus
- 2× glass
- 1× scissors
- 2× wooden skewer or pencil
- 2× clothes peg
- 1× newspaper to protect the table
Frequently asked questions
- Why does it work?
- Water creeps up between the tiny fibres of the paper by capillary action, dissolving the ink's pigments and carrying them along. Pigments that dissolve better in water and cling less to the paper travel further — so the mixture separates into its components. Laboratories use the very same principle to identify substances.
- Why does it not work with permanent markers?
- Permanent marker ink does not dissolve in water, so the water cannot carry it along. Stick to water-based markers — they guarantee the show.
- Why should I label the strips in pencil?
- Pencil graphite does not dissolve in water, so the label stays put. If you wrote with a marker, the label itself would start climbing and blur into the chromatogram.
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Every version of this image is kept. Nothing here was photographed in a lab — the illustrations are generated on ATAILA hardware, and when the models or the prompt improve we regenerate and keep the old one so the difference is visible.