Non-Destructive Paper Chromatography Forensic Ink Analysis
A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.
Materials Needed
- • Black pens of different brands (gel, felt, ballpoint) (4 pens)
- • White lab filter paper or flat unbleached coffee filters (2 sheets)
- • Rubbing alcohol and water mix (1/2 cup)
- • Tall clear glass and binder clips (1 set)
- • Metric millimeter ruler and pencil (1 set)
Pro Tips
- → Have a partner write a mystery "ransom note" using one of the four numbered black pens while your child is out of the room.
- → Calculate the Retention Factor (Rf value): divide the distance traveled by a specific color band by the total solvent front distance.
- → Show how two pens that both look solid black on paper actually separate into completely distinct dye formulations.
Safety First
Work in a well-ventilated room when using rubbing alcohol; keep liquids away from eyes.
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Step-by-Step Instructions
Step 1
Cut four 2 cm x 12 cm filter paper strips and draw a baseline pencil line 1.5 cm from the bottom of each strip.
Step 2
Spot a small, concentrated dot of ink from Pens A, B, and C onto separate strips; spot a dot from the "crime note" onto strip 4.
Step 3
Suspend all four strips simultaneously into a glass containing 1 cm of a 50/50 water-alcohol solvent mix, ensuring the ink dots stay above the liquid line.
Step 4
Allow the solvent front to climb 8 cm, mark its final height, and measure Rf values for the separated blue, pink, and yellow bands to identify the matching pen.