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The Challenge: Make Paper and Ink

Now for the ink and pens. How is ink made?

Our ink was created by the chemical reaction between tannic acid and iron sulfate in an aqueous solution. The primary active components in tannin are gallotannic and gallic acid. With iron (II) sulfate, these tannic acids produce a black pigment upon exposure to oxygen. A small amount of pigment forms by reacting with oxygen in the water but much more pigment is produced after the ink has been applied to paper and exposed to air for several hours. We also used a small amount of sticky cherry juice as a thickening agent and binder.

Rough Science pigments