Book of Secrets

Title page, L'Arte Vetraria,
by Antonio Neri (1576-1614)

Today, we recognize L'Arte Vetraria as the first printed book devoted to the art of glass formulation. It is a work committed to the subject of refining raw materials and combining them into a variety of glasses, over a rainbow of colors. 'First in print' is a notable distinction, but one that Neri surpassed with ease through a deeper accomplishment. His book provides a rare glimpse of skilled practical knowledge. This was an era when prized techniques were often lost to subsequent generations because artisans so often spared the pen. Their precious knowledge was kept far away from paper, passing in strict confidence from master to apprentice working side by side. Trade secrets were guarded possessions. Recipes committed to writing were an invitation for prying eyes—in the case of virtuoso glass, an invitation to be compromised by individual competitors and by rival states. This is what makes Neri’s book of glassmaking recipes extraordinary. In an age of secrecy, L'Arte Vetraria was a deliberate exposition, a lucid guide to the art by a seasoned professional. He intended it for the enlightenment of those with no other qualification than a "kind and curious spirit." He assures us that "given a bit of experience and practice, as long as you do not foul-up on purpose, it will be impossible to fail." 

Books of secrets have been a part of our culture since history began. More than the mysticism they imply, they chronicle the development of various technologies and show us in a literal sense how we got to where we are today. They play a unique role in preserving types of knowledge taught by doing. For one practiced in a particular art, a book of secrets was a roadmap, sequencing new steps on a landscape that was already familiar. Neri's L'Arte Vetraria is a prime example of this genre; it documents the chemistry of glassmaking in the late Renaissance and it highlights the link between alchemy and the arts. But Neri takes on an increased challenge by inviting the novice to partake in his craft. He created a document that spoke to the uninitiated of his own time and still speaks to us today. Neri and the other masters of his day may be long gone, yet his painstaking, jargon-free instructions tell us with exact language what those master glassmakers were doing. 

Be warned in particular to give careful consideration to the colors for which exact and determined amounts cannot be given. Indeed, with experience and due practice learn and with the eye and judgment know when a glass is colored sufficiently and appropriately for the work at hand. 

These books have unique characteristics that distinguish them from other forms of writing. The author must have one foot in the learned world of letters and the other foot in the intuitive world of craft. Working at the Casino di San Marco and elsewhere, Neri and his fellow artisans think in images, smells and textures. They have a first-hand detailed experience that does not lend itself to written words with ease. The essence of an artisan's work defies accurate capture between pages, yet Neri verbalizes these procedures in a clear narrative. When he cannot give exact amounts, he explains with care the decision making process that must take place.

"With this, I do not rely on either dose or weight, but only on my eyes. When I see that the glass reaches the desired level of color, I stop adding salt." From the contents of his glass recipes, we can see his bottom-up thinking. He starts with details gained from hands-on experience and forms his conclusions based on that knowledge. In sharp contrast to other authors of the period, Neri presents no grand theories of nature. Nor does he struggle to fit glass into a larger abstraction. Many contemporaries debated at length over the true essence of glass—whether it was more like metal or mineral and therefore possessed one set of essences over another. Perhaps more significant, Neri does not impose extranatural explanations on the results of his chemistry; instead he follows nature. The top-down approach is not his way, he interacts with his materials, he observes how they behave and he encourages the desired result by optimizing favorable conditions. 

On a practical level, alchemists interacted with nature to transform materials in ways other arts could not. Sculptors could use physical tools to transform a block of marble into a statue, but the substance of the marble was unchanged. Ironsmiths could forge a suit of armor and weavers could transform fibers into cloth. However, it was alchemists who made the fabric dyes permanent. It was alchemists who could dissolve a block of marble with reagents before one's eyes. To common men and women, the alchemist's world of transmutation must have seemed magical. Books like Neri’s gave a glimpse into the real-world mechanics of these mysterious arts.