[5] Gallic acid forms intermolecular esters (depsides) such as digallic and cyclic ether-esters (depsidones).

Pliny the Elder (23–79 AD) describes the use of gallic acid as a means of detecting an adulteration of verdigris[7] and writes that it was used to produce dyes.

It could then be mixed with green vitriol (ferrous sulfate)—obtained by allowing sulfate-saturated water from a spring or mine drainage to evaporate[citation needed]—and gum arabic from acacia trees; this combination of ingredients produced the ink.

[8] Gallic acid was one of the substances used by Angelo Mai (1782–1854), among other early investigators of palimpsests, to clear the top layer of text off and reveal hidden manuscripts underneath.

Mai was the first to employ it, but did so "with a heavy hand", often rendering manuscripts too damaged for subsequent study by other researchers.

[15] Gallic acid is also found in various oak species,[16] Caesalpinia mimosoides,[17] and in the stem bark of Boswellia dalzielii,[18] among others.

Many foodstuffs contain various amounts of gallic acid, especially fruits (including strawberries, grapes, bananas),[19][20] as well as teas,[19][21] cloves,[22] and vinegars.