How a simple piece of kitchen roll reveals the secret ingredients of ink
In short: Two pens might look identical to the naked eye, but they could be composed of entirely different color palettes. Through the scientific technique of chromatography, you can unmask these hidden pigments, using nothing more than water and a paper towel to solve a colorful mystery.
Chromatography is a scientific technique used to separate the various components of a mixture. In a home setting, this can be achieved using non-washable felt tip pens, water, and kitchen roll. The process relies on the principle that different colored inks are actually mixtures of several different colors. When water is drawn up through the paper, it acts as a carrier for these pigments. This activity is part of the ExpeRimental series, which features accessible science for children aged 4 to 10. It is a project supported by the Royal Society of Chemistry.
The separation occurs because the different pigments are made up of different-sized molecules. As the water spreads through the tissue, it carries these molecules at different rates. Because these molecules vary in size, they travel different distances across the paper, effectively unmasking the individual colors that were blended to create the original shade. This creates a beautiful visual record known as a chromatogram.
This experiment serves as a practical way to observe the properties of solids, liquids, and gases, specifically focusing on solubility and how mixtures can be separated. By observing how far each pigment travels, learners can compare and group everyday materials based on their physical properties. While simple, the method can be used to solve mysteries, such as identifying which specific pen was used to write a particular letter by matching the unique color patterns revealed by the water. Prior to food preparation, always wash all tools completely to maintain safety. It is also recommended that an adult provides supervision or direction during the process.
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Sources
- Summary by Intellect · source: At home science - Coloured pens experiment - ExpeRimental #11
- Also: Kitchen roll chromatography
- Also: DIY Chromatography
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