Neri’s host, Emmanuel Ximenes, owned several titles by this somewhat obscure figure. Historians conjecture that there were actually two alchemists in the Hollandus family, Isaac and Johannes Isaac. Their relationship is not clear, although they are often assumed to be father and son. We know little about them; some authors date them as early as the fourteenth century. However, a preponderance of evidence point to about the time Neri lived. In his glass book, in the fifth part devoted to artificial gems, Neri writes:
Above all is this wonderful invention. A new way practiced by me, with the doctrine taken from Isaac Hollandus, in which paste jewels of so much grace, beauty and perfection are made, that they seem nearly impossible to describe and hard to believe.
Now, we might also ask about the actual recipe that Neri was using. We have his version, but what about the original by Hollandus? It is an important historical question because Neri's version went on to be reprinted, copied, and plagiarized possibly more than any other glass related technical recipe in the 17th, 18th, and 19th centuries. One Hollandus title in Ximenes' Antwerp library was Opera Mineralia, first published in 1600. The subject of this volume is the philosopher's stone and its production. While there are no artificial gem recipes here per se, there are some intriguing connections between artificial gems and the philosopher's stone, both philosophical and practical. It was thought that the colors of metallic based glass pigments were an indication that the metals were "opened" and became susceptible to alchemical transmutation. Of special interest was the deep red ruby color made by adding gold to the glass melt. In the introduction to a 1797 French translation of Neri's book, artificial ruby or "vitrified gold," is equated to the bible's Electrum of Ezekiel —a red glow seen by the prophet in a vision.
By the mid-eighteenth century, Isaac Hollandus was lauded in industrial arts books as a genius of artificial gems. He may well have been, but the evidence does not support it. All of the specific recipes attributed to Hollandus seem to lead back to Neri's L'Arte Vetraria or its translations. A case can be made that Hollandus' reputation for artificial gems stems from a 1697 plagiarized version of Neri's book. A volume published in
France by Haudicquer Blancourt that gives no credit to the Italian priest. Blancourt used Christopher Merrett's English edition of Neri as his base and added to the recipes with his own embellishments. The chapter on artificial gems still lauds Hollandus, but its length was now doubled from Neri's original set of seventeen recipes to thirty-five. Each the same basic formulation with different pigments added to simulate different gems. The size of this one section jumped from thirteen to nearly two hundred pages, an increase in page-count larger than Neri's entire book. He was adding pages, but not much new content. The expansion was accomplished largely by inserting the full base glass recipe into each color, and then expand the color range. In 1699, Blancourt's version was then translated back into English, again without reference to Neri. There is no doubt that these two editions, with their expanded chapters on paste gems exerted a strong influence on later craftsmen. They may also be the source of the credit given to Hollandus' for paste gems in the eighteenth and nineteenth centuries.
A number of intriguing questions remain unanswered. Chief among them is the nature of Neri’s association with the Dutch alchemist(s). Was Hollandus or his son (or brother, or cousin) alive in the first decade of the seventeenth century and did Neri meet with either of them in person? We can only guess. The Hollandus men are notable, if not enigmatic, characters in the transition from alchemy to modern chemistry. Historians would very much like to know them better. Nevertheless, there can be no doubt of the strong impact Hollandus made on Neri. Isaac holds a singular honor as the one person named in Neri's book to whom he gives specific credit. As research on early modern science has progressed, the importance of communication between practitioners has emerged as a central theme. A meeting of the minds between Neri and Hollandus, if it ever occurred, would rank as a prime example of technology transfer with a definite impact.
For a comprehensive look at Hollandus see: Annelies van Gijsen, "Isaac Hollandus Revisited" in Chymia: science and nature in Medieval and early modern
Europe, Miguel Lòpez-Pèrez, Dider Kahn; Mar Rey Bueno, eds., ( : Cambridge Scholars, 2010), pp. 310–324. Newcastle upon Tyne, UK
*This post first appeared here 2 April 2014.
*This post first appeared here 2 April 2014.