In early 1603, Glassmaker Antonio Neri traveled from
to Flanders, to visit his friend Emmanuel Ximenes. Neri
would stay for seven years and in that time he worked on a number of glass
related projects including the manufacture of artificial gems using lead
crystal glass. An enduring mystery is that in his glass book L'Arte Vetraria, he gives credit to alchemist Isaac Hollandus for
a "new chemical method never before used," yet no such recipe for artificial
gems has ever been found in the writings of Hollandus.
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.
In the 1679 German edition of L'Arte Vetraria, Johannes Kunckel implies that Isaac was dead before Neri came to Antwerp, writing "This is the manner to imitate precious stones, of Isaac Hollandus, (namely, from his posthumous writings) that I [Neri] learned in Flanders" (emphasis added). Yet, coinciding with Neri's visit, playwright Ben Jonson who had just returned to
from the war in Flanders, referenced the pair in his
satirical work The Alchemist (1610).
There he implies that the elder Hollandus was then dead but survived by "living
Isaac." In 1644, the famous Flemish chemist Van Helmont identified Isaac
Hollandus as a recent contemporary. In a 1716 treatise, Kunckel paid Hollandus
a great compliment and at the same time took a swipe at Helmont saying "and the
incomparable Hollandus had more of the fire-art in his little finger as Helmont
in his whole body." In another reference, Sir Francis Bacon mentions Hollandus
as "by far the greater part of the crowd of chemists."
One Hollandus title in Ximenes'
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
by Haudicquer Blancourt that gives no credit to the priest. Blancourt used
Christopher Merrett's English edition 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 the seventeen original recipes to
thirty-five. 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. 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 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