By Jon Storm, Co-Director of Publicity & Social Media
Have you ever noticed a strange round growth on an oak leaf or branch and wondered what caused it? You likely found a gall, an abnormal growth of tree tissue caused by a wasp, mite, or aphid. Many species of gall-making insects begin life as eggs laid in oak leaves or branches. The gall provides both shelter and food for the developing larva over the following weeks or months.
The United States Declaration of Independence. By archives.gov, Public Domain, Wikimedia Commons.
While galls may seem like little more than odd growths on a tree, they have played an important role in America’s history. For centuries, a by-product of oak galls was used to make the ink found in documents ranging from the Magna Carta and Leonardo da Vinci’s drawings to Beethoven’s handwritten musical scores and the United States Declaration of Independence.
Oak galls were only one ingredient, though. Ink makers typically combined tannins from the galls with iron from rusty nails, gum Arabic, and sometimes even beer or wine. When tannins and other compounds extracted from soaked oak galls were mixed with iron, they produced dark, long-lasting ink that flowed easily from a quill.
The oak galls used by the Founding Fathers likely didn’t come from oak trees native to the Colonies. Most iron gall ink came from galls on the Aleppo oak (Quercus infectoria) of southern Europe and the Middle East. Because these galls have a particularly high tannin content, they were used to make ink for centuries before the Declaration of Independence. So, the next time you spot a gall on an oak tree, remember that similar growths once helped produce the ink used to write some of history’s most influential documents.
References
https://www.archives.gov/publications/prologue/2016/fall/declaration
https://www.amphilsoc.org/blog/ins-outs-iron-gall-ink
Eiseman, C. and N. Charney. 2010. Tracks & Sign of Insects and Other Invertebrates: A Guide to North American Species. Stackpole Books, Mechanicsburg, PA.
