Iron Gall Ink

Friday, March 17th 2023

Iron gall ink is a type of ink that has been used for centuries and is known for its durability and permanence. It is made by combining tannin extracted from oak galls with iron salts, such as ferrous sulfate or iron chloride. The resulting ink is a dark blue-black color and is highly resistant to fading and water damage.

Iron gall ink has a long history of use in Europe, where it was the primary writing ink for many centuries, from the medieval period through to the 19th century. It was also used in Islamic and East Asian calligraphy. Iron gall ink was eventually replaced by other types of ink, such as synthetic dye-based inks, because of its tendency to corrode paper over time.


If you are interested in making your own iron gall ink, here is a basic recipe that you can try:


  • 100 grams of powdered oak galls
  • 50 grams of ferrous sulfate
  • 1 liter of water
  • Gum arabic (optional)


  1. Crush the oak galls into a fine powder.
  2. Mix the oak gall powder with water and bring to a boil. Simmer for about 30 minutes to extract the tannin.
  3. Strain the liquid through a cheesecloth or coffee filter to remove any solids.
  4. In a separate container, dissolve the ferrous sulfate in water.
  5. Slowly add the ferrous sulfate solution to the oak gall extract, stirring constantly.
  6. Let the mixture cool and settle for several hours or overnight.
  7. Pour off the clear liquid on top of the settled sediment and store in a sealed container.
  8. Add gum arabic as a thickener, if desired.

Note that iron gall ink can be corrosive to certain types of paper, especially if the ink is made with too much iron sulfate. It is important to use a recipe that has been tested and to use the ink sparingly to avoid damage to your paper. It is also recommended to use a dip pen or a dedicated pen for iron gall ink, as it can cause corrosion and clogging in fountain pens over time.

Ferrous sulfate

Ferrous sulfate, also known as iron sulfate, can be purchased from chemical suppliers, online retailers, or in some cases, hardware or gardening stores. It is commonly used as a nutritional supplement and a soil amendment for plants, so it may be available in garden centers or agricultural supply stores as well. When purchasing ferrous sulfate, be sure to check the purity and grade of the product, as some forms may be unsuitable for ink-making purposes. It is also important to handle ferrous sulfate with care, as it can be toxic if ingested or inhaled.

About biocides

When making your own iron gall ink, it is important to use a biocide to prevent the growth of mold and bacteria in the ink over time. Some commonly used biocides in ink-making include:

  1. Thymol - a natural compound derived from thyme oil that is effective against a wide range of microorganisms.

  2. Sodium benzoate - a food-grade preservative that is often used in cosmetics and personal care products.

  3. Chlorhexidine - a broad-spectrum antimicrobial agent commonly used in healthcare settings.

  4. Isopropyl alcohol - a disinfectant that is effective against many types of bacteria and fungi.

  5. Formaldehyde - a potent biocide that is highly effective but can be toxic in high concentrations.

It is important to follow proper safety precautions when handling biocides, as some can be toxic or hazardous to your health. Always use biocides in well-ventilated areas and wear appropriate protective equipment, such as gloves and safety goggles. Additionally, be sure to carefully follow the instructions provided by the manufacturer and use the appropriate dosage for your ink recipe.