Lesson: Making Iron Gall Ink
This lesson covers the process of making iron gall ink, a widely used ink from antiquity through the Middle Ages. In ancient times, particularly in the Western world, the most commonly used ink was carbon-based. This ink was simple to produce, consisting of crushed carbon mixed with a binder, often gum arabic.
In the Middle Ages, iron gall ink emerged as an alternative. One of the key advantages of iron gall ink is its ease of production, as well as its permanence. While carbon-based inks can be washed off or erased from parchment or paper, iron gall ink is highly permanent, making it particularly useful for legal documents.
The ink is made using two main ingredients: tannic acid, commonly derived from oak galls, and iron sulfate. Oak galls, which grow on oak trees, are crushed to extract the tannic acid. The crushed galls are soaked in water for about a day to allow the tannic acid to infuse into the water. After filtering this solution, it is mixed with iron sulfate, known historically as green vitriol.
The resulting solution is initially brownish but turns black when iron sulfate is added. The reaction produces a ferrous tannate complex, which is water-soluble and can be applied to paper or parchment. When exposed to oxygen, the ferrous tannate oxidizes to form ferric tannate, which is not water-soluble and behaves like a pigment. The ferric tannate particles bind with the paper, giving the ink its characteristic permanence.
The earliest known reference to iron gall ink comes from the Roman writer and philosopher Caius Plinius Secundus (Pliny the Elder), who described an experiment where papyrus soaked in tannin would turn black when iron sulfate was applied, marking the first historical mention of the ink-making process.
Objectives:
- Understand the historical significance of iron gall ink.
- Learn about the basic ingredients and chemical processes involved in its creation.
- Gain hands-on experience in preparing iron gall ink.
- Compare iron gall ink to earlier carbon-based inks, emphasizing its permanence and resistance to erasure.
Materials:
- Oak galls (source of tannic acid)
- Iron sulfate (green vitriol)
- Water
- Coffee filter (or similar for straining)
- Mortar and pestle for crushing oak galls
- Container for mixing
Lesson Plan:
- Introduction to Iron Gall Ink
- Brief history of ink in antiquity: carbon-based ink was widely used by the Greeks and Romans.
- The transition to iron gall ink in the Middle Ages and its widespread use for legal documents due to its permanence.
- Chemical Properties of Iron Gall Ink
- Discussion on tannic acid from oak galls and its reaction with iron sulfate.
- Explanation of ferrous tannate (soluble) turning into ferric tannate (insoluble) upon oxidation, creating a permanent ink.
- Step-by-Step Preparation of Iron Gall Ink
- Crushing oak galls to extract tannic acid.
- Soaking galls in water for 24 hours to release the tannic acid.
- Filtering the solution to remove solid particles.
- Adding iron sulfate to the tannic acid solution to produce black ink.
- Hands-On Ink Creation and Writing
- Participants create their own iron gall ink following the demonstrated steps.
- Discussion of the oxidation process where ferrous tannate transforms into ferric tannate, bonding permanently with paper.
- Historical Context: The Experiment of Plinius the Elder
- Reference to Gaius Plinius Secundus (Plinius the Elder) and his early description of the reaction between tannin and iron salts.
- Demonstration of the blackening of papyrus when treated with tannin and iron sulfate, as described in Plinius’ writings.
- Conclusion and Discussion
- Recap the properties that make iron gall ink so permanent.
- Open discussion on the uses of iron gall ink in historical and modern contexts.
