How to Make Medieval Ink from Oak Galls and Iron
Oak-gall ink was one of the most important writing materials in medieval Europe. Made from tannin-rich oak galls, iron salts, water and gum, it produces a blue-black liquid that darkens as it dries. Scribes used related recipes for manuscripts, accounts, legal records and personal letters, although the proportions varied according to local materials and preferred writing styles.
For Australian reenactors, the project offers a practical way to connect a living-history activity with historical craft. The ingredients are accessible, but the process needs care: iron salts can irritate skin, tannin solutions stain intensely, and a poorly balanced batch may become corrosive over time. The medieval community directory can help place this craft alongside events, workshops and historical demonstrations.
Understanding The Historical Recipe
Oak galls are abnormal growths formed when certain wasps lay eggs in oak tissue. The tree responds by producing a hard, knobbly structure containing a high concentration of tannins. These tannins react with iron salts to create the dark compound that gives iron-gall ink its characteristic colour.
Traditional recipes commonly combined powdered oak galls, iron(II) sulfate, gum arabic and water. Iron(II) sulfate is often sold as ferrous sulfate, green vitriol or copperas. Gum arabic acts as a binder, helping the ink flow from a quill and adhere to parchment or paper. Some historical recipes also included wine, vinegar or other additives, but a simple water-based mixture is easier to control.
The exact appearance depends on the galls, the iron salt and the time allowed for oxidation. Freshly mixed ink may look grey, violet or pale brown before turning darker in contact with air. A modern recreation should aim for the character of the material rather than assume every medieval batch was identical.
Gathering And Preparing Materials
Use dried oak galls from a reputable craft supplier, specialist historical-materials shop or a clean fallen branch in an area where collection is permitted. Oak galls may be difficult to find in Brisbane or Perth compared with Melbourne and Sydney, where craft and historical-reenactment markets are often more varied. Do not collect from protected parks, private land or heritage plantings without permission.
Australia’s biosecurity rules also matter. Imported plant material can carry insects, fungi or soil, so oak galls brought from overseas should be checked against current Australian requirements before purchase. Local suppliers reduce that risk and make it easier to identify what has been treated. Avoid galls that are mouldy, damp, chemically dyed or covered in soil.
You will need a non-metallic jar, a small kitchen scale, a pestle or hammer, fine cloth or coffee filters, glass storage bottles, distilled water, gum arabic and ferrous sulfate. Keep these tools separate from food equipment. In a typical home in Adelaide, Canberra or Hobart, a cool cupboard is preferable to a sunny windowsill, particularly during warm weather.
| Material | Practical amount | Purpose |
|---|---|---|
| Crushed oak galls | 20 g | Supplies tannins |
| Distilled water | 200 ml | Extracts the tannins |
| Ferrous sulfate | 10 g | Reacts with the tannins |
| Gum arabic | 5–10 g | Improves flow and adhesion |
| Clove or preservative | Optional, minimal | May slow spoilage |
Making The Ink Safely
Begin by crushing the dried oak galls into coarse fragments or a rough powder. Place them in a glass jar with 200 millilitres of distilled water and leave the mixture for several days, shaking it once or twice a day. A longer extraction, lasting one to two weeks, generally produces a stronger colour. Strain the liquid through cloth, then filter it again until most particles have been removed.
Dissolve the ferrous sulfate separately in a small amount of distilled water. Add it gradually to the strained gall extract while stirring with a glass or wooden tool. The liquid should darken fairly quickly. If it becomes almost black immediately and forms heavy sediment, too much iron may have been added; an excess can make the finished ink harsh and damaging to paper.
Prepare gum arabic by dissolving it in warm distilled water, then add a small amount to the iron-gall solution. Start with about five grams for this batch and increase only if the ink feels too watery or fails to remain on the writing surface. Let the mixture settle overnight, filter it again, and transfer it to a labelled glass bottle.
Wear gloves and eye protection when handling ferrous sulfate. Work in a ventilated area, keep the liquid away from children and pets, and wash splashes from skin promptly. Never store the ink in a metal container, since iron compounds can react with the container and alter the mixture.
Testing Colour Flow And Permanence
Test the ink on several surfaces before using it in a demonstration. Smooth cotton paper, handmade paper, parchment-style sheets and genuine parchment will absorb it differently. A quill may need a slightly thinner ink than a dip pen, while a broad reed pen may benefit from a more fluid mixture.
Allow test strokes to dry for at least 24 hours. Good iron-gall ink often begins grey or bluish and becomes deeper as it oxidises. Hold the paper at an angle to check for feathering, surface cracking or excessive show-through. If the line is too pale, allow the ink to oxidise longer before changing the recipe. If it is too thick, add distilled water a few drops at a time.
For public demonstrations at a market or festival, display a modern safety label and keep the working bottle behind the table. A historic-looking setup can still use contemporary precautions. The German festival guide offers useful context for the type of immersive environment where scribal crafts, armour and material culture are commonly presented together.
Storing And Using The Finished Ink
Iron-gall ink is best kept in a small glass bottle with a secure cap and a label showing the ingredients and date. Leave a little air space rather than filling the bottle to the brim, and inspect it regularly for mould, unpleasant odour, heavy sediment or unusual separation. Refrigeration is not essential, but a cool, dark cupboard helps slow deterioration in Australia’s warmer regions.
Avoid using a strong homemade batch on valuable manuscripts, family documents or archival photographs. Excess iron and acidity can contribute to paper degradation over many years, a problem known as ink corrosion. For display pieces, use good-quality modern paper or a conservation-approved substitute. A separate carbon-based writing ink is safer when long-term preservation matters.
For a living-history stall in Melbourne, Sydney or regional New South Wales, demonstrate the stages with labelled samples: dry gall, strained tannin extract, freshly combined ink and an oxidised writing test. Finish by explaining that medieval scribes adjusted recipes through experience rather than following one universal formula. To begin safely, weigh 20 grams of crushed oak galls and start the cold-water extraction in a labelled glass jar.