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Try this easy paper chromatography experiment to find out who wrote a secret note!
Did you know inks are mixtures of different coloured pigments? Chromatography is a technique used to separate a mixture into its different parts, based on the chemical properties of each component.
In this experiment, you’ll test the pigments in different pens. Then you can test your detective skills by matching a particular pen to a note.
What you’ll need
- 5 tester pens, must all be the same colour ink and the ink must be water soluble (this means that it dissolves in water)
- Filter paper, cut into 3cm x 12cm strips (you could use slow absorbing paper towels or coffee filter paper)
- 2 glasses or clear plastic cups
- Scissors
- Water
- Pencil and paper
Instructions
Prepare a note: Prior to this activity, have an adult take one tester pen and write you a note.
Note to adult: Make sure you don’t let on which pen you used!
Test the note
- Cut a strip from the note (approx. 3cm x 12cm) as evidence. For best results, cut a piece that has a question mark or other punctuation marks written on it.
- Fill one glass about halfway with water.
- Place the strip of note into the glass, with the bottom of the paper in the water.
- Fold excess paper over the side of the glass to hold the paper in place.
- Leave paper strip in place until the water has travelled half way along the paper or until the inks start to split into individual colours.
- Remove the paper from the water, place on a flat surface and allow to dry
Note: if you’ve written the message on ordinary paper, the chromatography process may take slightly longer to complete than the chromatography filter paper.
Test the pens
- Place the pens on a coloured sheet of paper, with labels A to E.
- Place a pen at each of A to E.
- Take a strip of filter paper.
- Select the first pen and draw a horizontal thick line approximately 2cm above the bottom edge of the paper.
- Using the pencil, make a note of the pen number at the top of the paper.
- Repeat Steps 3 to 5 for all pens.
- Fill the second glass about halfway with water.
- Place the first strip of paper (pen 1) into the cup of water, with the bottom of the paper in the water.
- Fold excess paper over the side of the glass to hold the paper in place.
- Leave paper strip in place until the water has travelled half way along the paper or until the ink starts to split into individual colours.
- Remove the paper from the glass, place on a white piece of paper and allow to dry.
- Repeat steps 8 to 11 for the other four pens.
Comparison
Compare the sample from the message with the results from the tester pens. Is there a match? Are there similarities in ink? Can you determine which pen wrote the note?
Looking for more activities to do at home?
