Because parchment, prepared from animal hides, is far more durable than paper or papyrus, most palimpsests known to modern scholars are parchment, which rose in popularity in western Europe after the sixth century. Also, where papyrus was in common use, reuse of writing media was less common because papyrus was cheaper and more expendable than costly parchment. But some papyrus palimpsests do survive, and Romans referred to this custom of washing papyrus. The reed from which it was made did not grow in Italy.
The writing was washed from parchment or vellum using milk and oat bran. With the passing of time, the faint remains of the former writing would reappear enough so that scholars can discern the text (called the scriptio inferior, the "underwriting") and decipher it. In the later Middle Ages the surface of the vellum was usually scraped away with powdered pumice, irretrievably losing the writing, hence the most valuable palimpsests are those that were overwritten in the early Middle Ages.
Medieval codices are constructed in "gathers" which are folded (compare "folio", "leaf, page" ablative case of Latin folium), then stacked together like a newspaper and sewn together at the fold. Prepared parchment sheets retained their original central fold, so each was ordinarily cut in half, making a quarto volume of the original folio, with the overwritten text running perpendicular to the effaced text.
Cultural considerations also motivated the creation of palimpsests. The demand for new texts might outstrip the availability of parchment in some centers, yet the existence of cleaned parchment that was never overwritten suggests that there was also a spiritual motivation, to sanctify pagan text by overlaying it with the word of God, somewhat as pagan sites were overlaid with Christian churches to hallow pagan ground. Or the pagan texts may have merely appeared irrelevant. Texts most susceptible to being overwritten included obsolete legal and liturgical ones, sometimes of intense interest to the historian. Early Latin translations of Scripture were rendered obsolete by Jerome's Vulgate. Texts might be in foreign languages or written in unfamiliar scripts that had become illegible over time. The codices themselves might be already damaged or incomplete. Heretical texts were dangerous to harbor: there were compelling political and religious reasons to destroy texts viewed as heresy, and to reuse the media was less wasteful than simply to burn the books.
Vast destruction of the broad quartos of the early centuries of our era took place in the period which followed the fall of the Roman Empire, but palimpsests were also created as new texts were required during the Carolingian renaissance. The most valuable Latin palimpsests are found in the codices which were remade from the early large folios in the seventh to the ninth centuries. It has been noticed that no entire work is generally found in any instance in the original text of a palimpsest, but that portions of many works have been taken to make up a single volume. An exception is the Archimedes palimpsest (see below). On the whole, Early Medieval scribes were indiscriminate in supplying themselves with material from any old volumes that happened to be at hand.
To the present day survived about sixty palimpsest manuscripts of the Greek New Testament. Uncial codices:
In planetary astronomy, ancient lunar craters whose relief has disappeared from subsequent volcanic outpourings, leaving only a "ghost" of a rim are also known as palimpsests. Icy surfaces of natural satellites like Callisto and Ganymede preserve hints of their history in these rings, where the crater's relief has been effaced by creep of the icy surface ("viscous relaxation"). They are characterized by fast projectile which penetrates the cold, icy crust. Inward flow of slushy surface causes the surface to retain this upflowing of water from the past.
In medicine it is used to describe an episode of acute anterograde amnesia without loss of consciousness, brought on by the ingestion of alcohol or other substances: 'alcoholic palimpsest'.
Several historians are beginning to use the term as a description of the way people experience times, that is, as a layering of present experiences over faded pasts.
Palimpsest is beginning to be used by Glaciologists to describe contradicting glacial flow indicators, usually consisiting of smaller indicators (ie striae) overprinted upon larger features (ie stoss and lee topography, drumlins, etc).
Architects imply palimpsest as a ghost —- an image of what once was. In the built environment, this occurs more than we think. Whenever spaces are shuffled, rebuilt, or remodeled, shadows remain. Tarred rooflines remain on the sides of a building long after the neighboring structure has been demolished; removed stairs leave a mark where the painted wall surface stopped. Dust lines remain from a relocated appliance. Ancient ruins speak volumes of their former wholeness. Palimpsests can inform us, archaeologically, of the realities of the built past.
Thus architects, archaeologists and design historians sometimes use the word to describe the accumulated iterations of a design or a site, whether in literal layers of archaeological remains, or by the figurative accumulation and reinforcement of design ideas over time. An excellent example of this can be seen at The Tower of London, where construction began in the eleventh century, and the site continues to develop to this day.
Archaeologists in particular use the term to denote a record of material remains that is suspected of having formed during an extended period but that cannot be resolved in such a way that temporally discrete traces can be recognized as such.
Egyptologists use the word for texts and representations inscribed in stone that have been scraped away, either completely or partially, often with a plaster filling being applied, and then a new inscription carved on top.