For more than a thousand years, the books of western Europe were written on the prepared skins of animals. Parchment - thin, flexible, and extraordinarily durable - was made by soaking raw hide in a lime solution, scraping it clean of hair and flesh, stretching it tight on a wooden frame, and smoothing it with a curved blade as it dried. The process, known in Latin as pergamena, produced a writing surface that has preserved the texts of the European middle ages in better condition than any other material could have done. Manuscripts nearly a thousand years old often appear as fresh, white, and supple as the day they were finished, and the physical survival of medieval literature is in large part the survival of the parchment that carries it.

The choice of animal matters. Sheepskin parchment is the commonest in most of medieval Europe, offering a balance of cost and quality. Calfskin, particularly the skin of unborn or very young calves, produces the finest white vellum, traditionally reserved for the most important books. Goatskin, more common in southern Europe and North Africa, produces a parchment with a distinctively visible grain. Modern analysis of surviving manuscripts has shown that different workshops preferred different animals, and the species choice can sometimes be used to identify the region of production when other evidence is ambiguous.

The preparation process was laborious. Raw hide, which decomposes within days, had to be processed quickly. Lime soaking, which typically lasted two to three weeks, loosened the hair so that it could be scraped off and initiated the chemical changes that would transform the hide into a stable writing surface. After scraping, the hide was stretched on a wooden frame and the moist skin was worked repeatedly with a curved knife called a lunellarium, which cut away thin layers as the skin dried. The parchment-maker had to judge the thickness accurately: too thick and the skin remained stiff and difficult to write on; too thin and it tore easily and became translucent. The British book historian Alice Warburton has described parchment-making as one of the most skilled crafts of the medieval period, requiring several years of apprenticeship to master.

A single large book required many sheets. The Codex Amiatinus, produced in England around 700 and now held in Florence, contains parchment from approximately two thousand individual animals. Producing a major illuminated manuscript was therefore a substantial agricultural and industrial undertaking, requiring a reliable supply of young animals, a workshop with experienced tanners, and many months of coordinated labour. The economics of book production reflected these costs, and medieval books were, in real terms, extraordinarily expensive objects. A parish priest of modest means would own perhaps two or three books; a wealthy cathedral library might hold several hundred.

The physical properties of parchment make it both durable and demanding. Parchment is hygroscopic: it absorbs and releases moisture with changes in atmospheric humidity, and it flexes measurably as it does so. A manuscript that is opened in a dry room and closed in a humid one will have changed shape slightly, and long-term cycles of wetting and drying can cause the binding to warp or the pages to cockle. Stable conditions of temperature and humidity are therefore central to modern parchment conservation. The tendency of parchment to retain ink is another of its virtues; ink sits on the surface of a well-prepared parchment rather than soaking into it, so the text remains sharp even when the page is flexed.

Modern studies have revealed information about medieval animal populations and farming practices that historical documents do not record directly. DNA analysis of the parchment of a surviving manuscript can identify not only the species of animal but, in some cases, the genetic relationships between animals in the same book, suggesting that several pages were produced from animals from a single farm or herd. Warburton's laboratory has used this method to trace the supply of parchment to several medieval scriptoria and has shown that some scriptoria relied heavily on local herds while others sourced parchment from much further afield. The information matches and sometimes extends what documentary evidence suggests.

The decline of parchment began in the late medieval period with the introduction of paper. Paper was cheaper, easier to produce in quantity, and better suited to the demands of moveable-type printing, which became dominant in Europe after 1450. By the end of the sixteenth century, parchment was restricted largely to legal documents and prestigious manuscripts, and by 1800 it had become a specialist material produced by a small number of workshops. Yet parchment never completely disappeared. A handful of workshops in Europe continued to produce parchment throughout the industrial era, supplying conservators, calligraphers, and the production of legal documents that by tradition required parchment rather than paper.

The last twenty years have seen a modest revival. The restoration of medieval manuscripts requires parchment of a similar quality to the original, and conservators have commissioned new production from workshops that still practise the traditional methods. Calligraphy communities, some of them associated with contemporary Islamic and Jewish traditions that continue to use parchment, have also supported a niche market. Warburton has observed that the survival of the craft is now dependent on a few specialists whose retirement would probably mean its loss, and that the transmission of skills to a new generation is an open question. The thousand-year-old technology that preserved the literature of the middle ages is thus itself now a heritage to be preserved, its future depending on the patience of institutions and individuals who value the direct continuity with the past that only a traditional craft can provide.