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Spinoza and Diamond Polishing?

What was Spinoza’s Relationship to the Gem and Diamond Trade

I post here a portion of a hard to find book, in the interest of establishing a baseline of information for others. Because this site has involved a variety of hypotheses on the kinds of influences Spinoza may have had, all should be sketched out as best we can. Among my thoughts as to the mystery of where Spinoza may have learned his lens-grinding craft, apart from any guild commitment, it occurs to me that he may have learned it, at least in part, through his involvement with the diamond trade. There is some evidence that Spinoza had dealings with gem dealers in the years 1655-56, in fact the scuffle and suit of Antonij Alverez shows that he and likely his family business had dealings with one of the largest Amsterdam diamond trade names, Duarte. Whether this engagement with the gem business led his curious mind into learning about the process of gem and diamond polishing from which he may have taken valuable techniques into his lens-grinding (using diamond dust as an abrasive) at this point we cannot say. All we can do is put the fact that Spinoza had unique skills, techniques and likely instruments for lens-polishing, as testified by Christiaan Huygens, and speculate if these come from an origin that would be specific to his Jewish community. These may have been techniques specific to gem polishing, a process which the Jews of Amsterdam predominately came to rule over, or they may have been specific to Jewish lens-grinding. In either case it may serve us well to lay out the facts of Jewish diamond trade during Spinoza’s young adulthood. At the very least such facts give us a broader picture of the time and place Spinoza grew up in, and one of the lathe-processes he would have at least in a cursory fashion been exposed to.

Jews of the Diamond City

The extensive quote below is from Jews of the Diamond City – Amsterdam (1988), put out by the Harry Oppenheimer Diamond Museum:

We hear of Jewish masterpolishers only from 1611 onwards. A notarial certificate from the year deals with a contract between Jewish diamond polishers who were trained by gentiles. A document dated 1615 mentions that one named Solomon Franco had finished his apprenticeship as diamond polisher with a certain craftsman named David Bolshnik. Additional sources in the first quarter of the 17th Century inform us about another dozen names belonging to Jews of Portuguese origin who were experts in diamond polishing. As a rule these craftsmen were poorer distant relatives of the merchants who imported the rough stones thus ensuring themselves employment and a decent income. For example, we know about the two famous families – Correal and Duarte de Paz – who gained their reputation as jewelers and diamond polishers in the 17th Century.

The waves of Jews who fled persecution from Germany and later the Jews who fled Poland and Lithuania after the massacres of 1648/9 lead to an influx of refugees lacking in means and profession to Amsterdam. Consequently, the social structure of the diamond industry underwent a gradual change; the Portuguese traders, the polishers and the jewelers became production managers who provided work for their Ashkenazi brethren who, to an increasing degree, constituted the working class.

In spite of the scant documentation of the period, it seems that the Portuguese Jews preferred their “Pollak” brothers over their gentile fellow-workers. It was their intention to teach them an “honorable” trade which would provide them with a reasonable income and standard of living.

Copper Etching Jan Luken (1690)

copper etching, Jan Luyken (1690)

It is interesting to consider what Jews saw in the polishing trade that made it so attractive to them. On a copper engraving by the Flemish artist Jan Luyken (1649-1712) a typical diamond polishing workshop is shown. It was a rather small room, dark and stiffling. The polisher stands near the polishing wheel and places the stone on the leaden head at the end of the polishing handle. Time and again he changes the position of the stone, each time choosing a different angle on the spinning iron wheel coated with diamond dust. The rotation of the wheel is affected by a transmission belt connected to a horizontal drive wheel.

A notarial certificate dated 1615 mentions that the Portuguese Jews employed gentile women to rotated the drive wheel; this it the first written testimony to a female work force in the diamond industry.

The Jewish polishers of Ashkenazi origin who were unable to employ gentile women had to employ their own wives and children to operate the wheel. Thus, day to day, from dawn to nightfall, the whole family labored 12 to 15 hours a day to make a living.

The diamond polishers in general, worked independently and received the raw material from the diamond traders. Their wages were determined according to a variable tariff based on the weight and quality of the rough stone, the form of the finished product and the quality of his work. However, these tariffs were also subject to supply and demand…

…Among all the occupations that flourished in the Jewish quarter of Amsterdam, such as peddling, printing, dispensing and others, the trade of “Diamond-schleifer” – Yiddish and Ladino word for diamond polisher -became “The Trade.” Every Jewish mother strived for her son to learn this trade which ensured him a secure future, a good livelihood and economic independence, but, above all, great mobility on the social scale.

To become a craftsman required a very high tuition fee (69-225 florins) collected by the master polisher. The training period to be an expert in all the stages of processing in the old fashionable shapes (heart, almond, rose-cut and brilliant), lasting from 15 months to four and a half-years.

Rough stones of good quality required only few preparatory stages before the polishing process: cleaving or sawing, (dividing the stone in two), and cutting, (rounding off the base). These operations were also taught by the master and only towards the 18th century can one observe the specialization in ancillary trades connected with the polishing (44-45), (Simona Edelman).

What We May Be Able To Glean

Aside from the thin hypothesis that Spinoza have have learned something from the diamond polishers of his community, there are significant facts in this brief piece. Unfortunately the text is not footnoted, so it is unclear what is an author’s conjecture and what has foundation. There is the idea that the Sephardic Jews had learned this trade from gentiles in the early part of the 17th century in Amsterdam. Henriëtte Boas places these to be Huguenot refugee’s from Antwerp, establishing one more Jewish and Protestant Reform attachment. (Yet I have also read that these techniques likely arose through a direct transmission with India, from whence the diamonds came.) Next we have a cost and a timetable set out for learning the trade. This gives clue to a non-guilded craft relationship, and may reflect upon lens-grinding as well. It is helpful to know that in 15 months a skill such as this one could be acquired for a fee. Interesting is the shift in labor distribution in the decade leading to Spinoza’s majority, as Ashkenazi started to form a “working class” in the diamond trade. One wonders if such an influx may have also opened the door to Spinoza learning lens-grinding in his community outside of the usual transmissions of knowledge, since economic relationships were changing. Additionally, we hear of the diamond dust and flat iron wheel, a material technique not mentioned in any of the lens-polishing techniques I have read in the period. Could it be that there is some improvement offered by this means? The leaded head in diamond grinding (pictured below), actually presents a semi-automated system of grinding that pre-dates any assisted lens-grinding of the time. Could the diamond-polisher’s example, (aided by the fact that he needed to make plane-cuts, and not spherical), have been the inspiration for some of the semi-automated ideas for lens-grinding, such as those by Christian Huygens, D’Orleans and Hooke? (And, is Spinoza’s rejection of assisted polishing related to the spherical shape itself, feeling that the hand bests can feel a spherical relation?). And lastly, the wheel is quite distinct from a lens-grinder’s wheel, in that the grinding is done at the edge, and not in a bowl form. Would this kind of wheel use have helped grind certain small sized lenses? Enough with the conjecture for the moment.

Jewish polisher, late 1800s

Jewish polisher, late 1800s

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