How did Angelo Cardinal Mai use palimpsests to recover previously unknown Greek and Latin texts?

In the field of textual criticism, Angelo Cardinal Mai (1782–1854) made significant contributions by recovering ancient literature from palimpsests. A palimpsest is a manuscript where the original text has been erased or scraped away to allow the parchment to be reused for a new document, often for economic reasons or to prioritize religious texts over pagan ones.12

Because these early erasure processes were rarely completely effective, the original, underlying writing often remained partially visible beneath the later text. By identifying and analyzing these hidden layers, Mai was able to publish previously unknown Greek and Latin works, most notably a significant portion of Cicero’s De republica. While modern scholars now utilize advanced laboratory techniques like ultraviolet light to recover such texts, Mai’s work in the early 19th century was instrumental in expanding the corpus of available ancient literature through the systematic study of these recycled manuscripts.231