Two main families of black ink
For most of written history, the black ink on a page came from one of two sources. The first was carbon: very fine soot or charcoal-like particles suspended in a liquid. The second was a chemical reaction between plant tannins and iron salts, producing what is now called iron gall ink. They behave quite differently, and the difference explains a lot about how old documents look today.
Carbon inks
Carbon ink is the simpler of the two. Soot is collected from burning oil, wood, resin or similar materials, ground very fine, and mixed with a binder so that it flows from a pen and sticks to the surface. Gum arabic, a tree sap, is the binder most often mentioned for ink of this kind, and animal glue was used in some traditions. Water carries the mixture.
Such inks were used in ancient Egypt on papyrus and in China, where ink was often made into dry sticks that the writer rubbed with water on an inkstone. Carbon is chemically stable. It does not fade through light or age the way many dyes do, and the particles sit on the surface rather than reacting with it. The weakness is physical: on a smooth surface like parchment, a carbon ink can rub or flake if the binder is weak, and on papyrus or paper it can wash off with water if it never soaked in.
Carbon ink is generally associated with an early period, but it did not disappear. It remained in use alongside newer inks for many purposes.
Iron gall ink
Iron gall ink became dominant in much of Europe and the Middle East by the early medieval period and stayed in wide use into the twentieth century. The usual recipe had a few parts:
- Oak galls. These are growths on oak trees caused by insects, and they are rich in tannins and related acids.
- An iron salt. Often called vitriol in older recipes, it was typically iron sulfate.
- A liquid. Water, wine or vinegar were common choices.
- A binder. Gum arabic thickened the ink and helped it hold on the pen.
When the iron meets the tannins, a dark compound forms. Freshly made ink is often pale and darkens as it dries and reacts with air, which is why some recipes describe the ink going from gray to a deep brown-black on the page. Exact proportions varied by period and region, and many surviving recipes disagree, so it is best to treat any single formula as one example rather than a standard.
Why scribes liked it
Iron gall ink had real advantages. It soaked into parchment and paper rather than sitting on top, so it was hard to wash or scrape away without leaving a trace. That was useful for legal documents and records where alteration was a concern. It was also cheap, because its ingredients were widely available, and it flowed well from quill pens. Its permanence made it a standard choice for official use, and many famous manuscripts, letters and drafts are written in it.
The damage it could do
The same chemistry that made the ink hold fast can also slowly harm the page. Many iron gall inks contain an excess of acid or free iron, and over decades or centuries these can break down the cellulose in paper or the collagen in parchment. The result is sometimes called ink corrosion. Writing may turn brown, and in severe cases the paper along the lines can crack or fall out, leaving a lace-like effect.
How badly a document is affected depends on the recipe, the paper or skin, humidity and storage. Some old iron gall documents are in excellent shape, while others are fragile. Conservators generally treat the problem with care, and it remains an active field of study. Because the damage depends on so many factors, general claims about any one manuscript should be treated cautiously.
Later developments
In the nineteenth century, chemists began producing ink from new materials. Added dyes made iron gall ink show up blue as soon as it was written, which gave the familiar blue-black color. Later, advances in synthetic dyes brought a range of colored inks that were simpler to make and less aggressive toward paper. These dye inks were well suited to the fountain pen and, later, to the oil-based pastes used in the ballpoint pen. Factory production of ink also followed the same pattern as other industrial chemistry, moving from workshop recipes to standardized products.
Carbon never fully left the scene either. Modern black printing and drawing inks are often carbon-based, which shows how long-lived the oldest solution turned out to be.