Deadly Fumes

Antonio Neri handled very dangerous materials on a daily basis. He used strong acids, which if splattered could easily burn flesh, or cause blindness. He handled poisonous compounds containing arsenic, mercury and lead. If ingested, or inhaled as fumes these materials caused progressive, irreversible damage to internal organs and especially to the nervous system. There is no question that Neri did take chances with his health, but he was not naive. He knew very well many of the potential dangers and others he could well imagine. In chapter 74 of his book L'Arte Vetraria, he describes a way to tint rock crystal with beautiful colors. He wrote:

Take orpiment of that really tawny orange-yellow color and pulverize 2 ounces of this along with 2 ounces of powdered crystalline arsenic, 1 ounce of pulverized crude antimony, and 1 ounce of sal ammoniac. […] Perform this entire operation under a large chimney to draw the fumes out of the room. These fumes are not only harmful but also quite deadly. Return to see if the coals have died down, because for the work to come out nicely, they must be burning well and full. For the remainder, leave and let the fire run its course with no one in the room with the work, for it is dangerous; the harsh materials will smoke quite a bit. Leave it to finish all fuming by itself and then extinguish the fire and spread the coals.

In the spring of 1603, Neri was working in Pisa and became seriously ill. The specific cause and symptoms of his ailment are not known. He could have been harmed by one of his own experiments, or just as easily fallen prey to an infection or one of many other maladies prevalent in the early seventeenth century. He postponed his planned visit to Antwerp in order to recuperate. Finally, on 2 May 1603, his friend Emmanuel Ximenes wrote: "Praise God that your indisposition has ended ... if the Pisan air is suited to your recovery then do not change it."

In the winter of 1603-4 Neri embarked on what would become a seven-year-long visit to his friend's palace in Antwerp. There, he would learn many new techniques, and ultimately have special glass vessels made and presented to Philip William, Prince of Orange. Upon his return to Tuscany in 1611, he sat down to write the book for which he is most remembered, L'Arte Vetraria. Two years after publication, in 1614, the priest would be dead. According to the only known account, printed over two centuries later by Francesco Inghirami, Neri fell ill and passed within a short time of unknown causes.

Lixiviation

Salsola Kali

A long time ago, perhaps as long ago as the Stone Age, our ancestors discovered that mixing water with the ashes from the previous night's fire makes a good washing-up liquid. Not the solids, but what dissolves in the water forms a mildly caustic lye solution. It cleans dirty hands, and oily hair. The more concentrated the lye, the more pronounced the cleansing effect. When the solids are strained out and the liquid is evaporated, left behind is a crystalline salt known as potash. This process of extracting the soluble components of charred plant material is known as lixiviation. Mix potash with tallow and you have soap, spread it on your fields and you have a good fertilizer, put it in a very hot furnace with powdered sand, and you have glass. In simple, everyday human activity we see the roots of modern chemistry. The English word ‘potash’ is derived directly from the process described above: made in a pot with plant ash. It lends its name to the chemical element potassium, a major constituent and a key ingredient for many glass recipes.

Besides potassium, plant ash can also contain significant quantities of sodium, magnesium and calcium. They occur in different amounts depending on the species and on its habitat. Plants are literally composed of the nutrients in the soil from which they grow. Mineral compounds that dissolve in water are brought in through the roots and become part of the plant. In northern European forests, salt from the ash of oak and beech trees and fern plants was used for potassium glass as far back as the middle ages. In the more arid Mediterranean regions, scrub vegetation from the coastal marshes made both sodium and potassium glass, namely with the soda and kali plants. The soda plant lends its name to sodium and the kali plant lends its name to a group of chemical elements, which we now call the alkali group. Of these two plants, salsola soda is high in sodium and very low in potassium, salsola kali is more equal between the two. The high sodium carbonate content of the soda plant and a few other species is unusual, but soda accounts for most glass made, even today. Most other plants are potassium rich. 

To make glass, the material was lixiviated: boiled, filtered, purified and dried. The raw plant material was lightly charred to reduce moisture content; this prevented rotting and reduced volume and weight significantly for shipping. Neri experimented with the ash of many other plants as well and he does not hesitate to mix salt from different sources to achieve a desired effect. He found suitable glass salts can be made from ferns, blackberries, broad bean (fava) husks, cabbage, thorn bushes, millet, rush and marsh reeds. What Neri did not know was that virtually all of these plants produced a salt that was heavily laden with potassium. Potash glass has a fundamentally different character than soda glass. He knew quite well that fern glass had a different workability and appearance from soda glass, but he was over a century too early to understand why. Highly purified, potash glass sparkles in the light more than soda glass. It is denser, giving better refraction of light, yet it is also more difficult to work since it stiffens quickly on the blowpipe.

Carries the Palm

Entry into Jerusalem, Pietro Lorenzetti 1320

In his book, L'Arte Vetraria, Antonio Neri presents a string of recipes for variations of green glass. Finally, in chapter 35, he presents his ultimate green, which he titles: "Another Green, Which 'Carries the Palm' for All Other Greens, Invented by Me." The phrase "caries the palm" alludes to the biblical story of Jesus entering Jerusalem, in which the people welcomed him by laying down cloth and palm branches on the ground in his path. Even before that, the palm branch served as a symbol of victory; in ancient Greece, palm fronds were awarded to victorious athletes. Later in history, Roman lawyers who won a case decorated their doors with palm leaves.

Saint Justina of Padua with a palm frond,
Bartolo Montagna 1490s

Cristallino was a mid-grade glass made with a soda based plant ash from the Levant called "rocchetta." For this recipe, Neri blends it with common glass, and adds red lead oxide to the mix, in effect forming an early version of what we now call lead crystal. He "cleans" the glass by using the well-established technique of flinging the molten glass into a large tub of clean water. This had the effect of "washing out" excess glass salt (flux). In addition, it provided the opportunity to sort through the fragments to remove any undissolved metallic lead. Lead that did not go into the glass had the tendency to collect at the bottom of the clay crucible. It could then eat a hole in the vessel, resulting in a glass-shop disaster, as he warns: 

All lead precipitating out of the glass must be removed with diligence, throwing it away, so that it does not make the bottom of the crucible break out, as can happen. Return the glass that was thrown in water to the crucible and leave it to clarify for a day. Then add the color using the powder, made chemically by the dry distillation of vitriol of copper [chapter 31]. Also, add a little crocus of iron, but very little. The result will be a most marvelous beautiful green, the best that I ever made. It will seem just like an emerald of ancient oriental rock, and you can use it in every sort of job.

Copper Sulfate (vitriol of copper)

Crocus of iron is simply iron oxide or 'rust' as it is more commonly known. The vitriol of copper he refers to is copper sulfate. Neri forms it in a laborious process that involves cutting copper sheet into small, coin-sized pieces, mixing it with sulfur, heating in the furnace and then reprocessing it several times. The result is then added to water and the soluble part is further processed, filtered and evaporated. The final product is a pure blue crystalline material that has uses for our alchemist that go far beyond glassmaking, as he alludes to in the final sentence of the book:

Although I have placed here the way to make this powder with much clarity, do not presuppose that I have described a way to make something ordinary, but rather a true treasure of nature, and this for the delight of kind and curious spirits.

Art and Science

Jacopo Ligozzi,1518,  ink and watercolor on paper.

Antonio Neri's writing on glassmaking and alchemy was distinguished from that of many contemporary authors in that his work was all deeply rooted in hands-on experience. His contemporaries were often content to repeat century's old teachings about the four Aristotelian elements; that chemical interactions could be predicted through an analysis of the balance between hot and cold, dry and wet. But more and more, these notions were being discarded and replaced. It is common to cite the invention of instruments, and other technical developments; these factors certainly did contribute to advancement. But many different forces worked toward the emergence of early modern science, and one in particular is so obvious that it is easily overlooked: artists.

Working with hot glass was a profession in which attention to nature was essential: artists did not have the luxury of fanciful explanations of physical processes. They were obliged by their work to learn the ways glass mixed, moved and behaved in the furnace, not as they imagined it should, but as it actually did. The only way to achieve the complex forms and vessels for which master glassblowers were renowned was through long experience. Failure to understand the glass and predict its properties accurately resulted in failure of the piece.

Neri was immersed in this environment and the same principles applied to his own work in formulating the glass. Ancient theories had little value if they did not accurately predict nature. Like the glass artists, the way forward for Neri was careful attention and hands-on experience. He learned the value of starting with highly purified ingredients for his glass melts. He learned that too much glass salt resulted in a putrid 'gall' that would need to be skimmed off the molten surface. Substituting salts made from fern plants, for the Kali based ones from the Levant, produced a more lustrous glass, yet it stiffened more quickly for the glassblowers.

A glass artist's work also serves as a kind of narrative. For those familiar with the techniques, a finished piece of glass work can be 'read' like a story: The handles were put on last, before that, perhaps a thin bead of color was applied to the lip of the vessel. And the work started as a blown bubble of glass, shaped and opened with special tools. Each step is an insight into the artist's technique, but also into the way nature itself operates. Each motion was a well practiced negotiation between the artist and the properties of the material.

On one hand, an artist's job was to produce objects contemplated for their physical beauty and cultural significance. On the other hand, the act of producing these objects created an environment where accurate scientific reasoning flourished. By collecting artists and employing them together, the Medici rulers of Tuscany were creating a cauldron effect where experiences collected, stewed and nature's secrets unraveled.

The Old Post Road

In the winter of 1603-1604, Antonio Neri left Italy to visit his friend Emmanuel Ximenes in Antwerp. There is no way to know the exact path he took, but based on the advice in Ximenes' letters and on well-established trade routes; a good estimation can be made. The path he suggested, if Neri was starting from Pisa, took the priest first back east to Florence, then perhaps through Bologna, Ferrara and Padua to Venice. Ximenes offered to make arrangements for Neri to travel from Venice with traders headed to the Frankfurt fair held at mid-lent. There would have been plenty of time for him to celebrate Advent in Florence and Christmas in Venice before his caravan headed north. The group could have left as late as the end of January.

Ximenes suggested that Neri travel with the courier from Florence to Venice. He was referring to the system of coaches that delivered the mail throughout Hapsburg Europe, run since the early 1500s by the De Taxis family. While the Medici and other heads of state maintained their own fast couriers for diplomatic and military messaging, the De Taxis had a monopoly on almost every other piece of correspondence, a privilege for the family that was later extended to other parts of the world. They ran an efficient system well into the eighteenth century. An elaborate series of posts were set up at intervals, where tired horses were watered and swapped for fresh steeds and riders so that the journey could continue uninterrupted. Independent travelers could partake in the system for a fee based on equipment required and the weight of luggage. In Neri's time, accounts were settled at each post and travelers could elect to stay over in a town and pick up a later expedition. On well-established popular routes like between Florence and Rome, travelers could pay a flat rate that included lodging and meals. If Neri had traveled light and spoke some German, he might have completed the entire journey in as little as ten days; the time letters from Venice to Flanders took to arrive.

On Embarking from Venice, the party of traders would head west, back to Padua, on to Verona and then north along the ancient trade route through Bolzano to the Brenner Pass. The journey from Venice to Frankfurt was about 600 miles (950 km). Traveling an average of 30 miles per day, they would be on the road for three weeks. Depending on their itinerary, the journey could have varied by a week in either direction. The start of the fair was mid-lent, the date of the traditional feast held three weeks before Easter. In 1604 mid-lent Sunday fell on 28 March.

Brenner is the lowest pass across the central Alps, connecting Bolzano on one side to Innsbruck on the other and was passable year round. The distance of this, most difficult part of the journey, was about 75 miles (120 km), with a vertical climb of 4,495 ft (1,370 m), almost a full mile, but all below the tree line. Assuming a slow pace for pack animals, this segment could still be completed in less than a week, stopping in Bressanone, (Brixen), then at the alpine city of Vipiteno (Sterzing), where perhaps some extra time was taken to rest and view the nearby silver mines. Gries am Brenner was just over the pass on the Austrian side. With the majestic Wipp valley (Wipptal) at their backs, the remaining journey was down hill from there. From Innsbruck, the traders would head towards Augsburg, perhaps with an excursion through Munich, which was then the capital of Bavaria. The route from Augsburg through Wurzburg to Frankfurt was riddled with small towns accustomed to hosting traders since Roman times. After a few weeks on the road, the fair at Frankfurt would have come as a welcome diversion.

At the end of the fair, a week before Easter, Neri would start the final 250 miles (400 km) of his journey. First, he would travel over land with merchants or the Ximenes family servant to the walled city of Cologne on the Rhine River. Next, he would move by water toward the sea. The northern route, along the Rhine, avoided the military conflicts between the Dutch Republic and the Hapsburg Empire. The most dangerous were between Liege and Antwerp. From Rotterdam, the inland waterways led south to Antwerp. Priest Neri may well have arrived in time for Easter Vigil.

Pisa

Majolica vase by Niccolò Sisti, 

decorated in the grotesque style.

In the early seventeenth century, there were several glass furnaces in Pisa. One was run at the pleasure of Grand Duke Ferdinando by Niccolò Sisti. Raised in Norcia in Perugia, he likely learned his trade at an early age;  Sisti's father, Sisto de' Bonsisti, was said to be an expert in making paste gems. This would account for the son's apparent skill in the medium of glass in addition to his ceramics prowess for which he was previously employed at the Casino di San Marco in Florence. For Neri, working at Sisti's glass house in Pisa played an important role in his glassmaking education. Sisti would serve three Medici grand dukes, Francesco I, Ferdinando I and Cosimo II. When work came to a stop at the Casino di San Marco, after Francesco’s death, Sisti may have opened his own factory in Florence for a short time, but then moved to a new facility in Pisa.

 In 1592, Grand Duke Ferdinando set up a glass shop in the central part of Pisa, along the north bank of the Arno River. This furnace was staffed by Muranese workers and was located in the city center, along the river. Archaeologists have unearthed its remains in the courtyard of what is now 43-44 Lungarno. The operation was capitalized with a loan of five hundred scudi made by Ferdinando I to Sisti, with a special mandate: he was to introduce new forms of pottery to the region. In addition to glass, the furnace at Pisa would produce soft-paste porcelain and majolica ceramics. These were both forms that Sisti had helped to develop when he worked in Florence at the Casino; he was involved in Francesco’s quest to duplicate Chinese porcelain.

In 1602, Neri was to be found working alongside Sisti at the Pisan furnace. According to his own account, this is where he worked on special colors, and collected river stones for glass frit. Here he made kermes based paints, enamels and used ferns as an alternative plant salt for glass. In all likelihood, he would have had access to the nearby botanical gardens and the small adjacent laboratory located just a few blocks from the glass furnace. 

Early in 1604, the priest would make his trip north to Antwerp to visit his friend Emmanuel Ximenes. During Neri's seven year absence, Sisti's projects included cristallo table service for the Vatican, and special glass for the lenses of Galileo's telescopes. Upon Neri's return from Flanders, we again find him working in Pisa, this time on alchemy. In a copy of his last known manuscript, a heading reads, "Techniques copied from an old book here in Pisa."  The university at Pisa was an intellectual center and a repository of technical knowledge. There, Neri had access to a wide range of materials in the libraries. The furnaces and laboratories provided him with hands-on experience, but there can be little doubt that he was a voracious reader as well. On the same page of this manuscript appears the date 26 January 1614. This is the last known specific information on the priest's whereabouts, since he would be dead within the year, at the age of thirty-eight.

Top Physician

In 1580, when Antonio was four years old, after the birth of his brother Vincenzio, both his father and grandfather were together granted full Florentine citizenship by Grand Duke Francesco I de' Medici. In Tuscany, citizen status was an honor conferred to a small fraction of the population and often through inheritance at around the age of thirty. The fact that Neri Neri gained citizenship at the age of forty and did so together with his father, Jacopo, shows it was not legacy, but perhaps their medical prowess that lead to the award. This period also corresponds to the first appearance of the unique coat of arms that distinguish this branch of the family. The same arms adorn the central panel of the vestibule ceiling at the Neri's residence. Citizen status bestowed the advantage of direct representation in the government and the right to hold public office. It also carried responsibilities to the city, to its leaders and to the Church. One requirement of citizenship was possession of a domicile within Florence. The baptism register listed Antonio and all of his siblings as residents of San Pier Maggiore parish long before the citizenship grant. However, it is in the 1580s that we see the first reference to Neri Neri's ownership of the palazzo at what is now 27 Borgo Pinti.

Within a few years, Antonio's father would publish his work on cures for paralysis and by the end of the decade he was appointed personal physician to the new grand duke, Ferdinando de' Medici. The 1590's saw Antonio taking vows, and beginning his career in the Church. The road to priesthood ran on a parallel track to an apprenticeship in a trade. The completion of a trial period lead to becoming a novice at the age of sixteen, then deacon and finally priest. Meanwhile, Antonio's father, along with another doctor and two apothecaries was chosen by the entire Florentine College of Physicians to revise and update the famed Ricettario Fiorentino. This book was the gold standard of doctors and pharmacists throughout Europe. The Ricettario was the official reference for medicinal cures in Tuscany. The law required every apothecary to own a copy and to supply its listed formulas to customers. Many regard this volume as the first European pharmacopoeia. It was a systematic standardization of drug recipes and dosages. Throughout the Medici reign, updated editions appeared as knowledge progressed. The book is a major landmark in the history of medicine. The edition authored by Neri's father and colleagues, in 1597, proved so popular that in 1621 it was reissued without change.

There can be no doubt that Antonio's father and his work had a profound influence on the priest. In his book on glassmaking, L'Arte Vetraria, he proclaims his desire to publish his own work on chemical and medical [spagyric] arts, saying "I believe there is no greater thing in nature in the service of humanity." In his recipes he uses the terminology of physicians; adding chemicals in 'doses' and measuring 'ana' (in equal parts). In a 1608 letter to a friend, Antonio describes his great success with medicinal cures of Paracelsus, "to the great wonderment of Antwerp." The priest also references experiments he carried out in Brussels and at the Hospital of Malines.