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How to be a blacksmith
What did Leeuwenhoek have to learn in order to use his little lenses?
Leeuwenhoek grew up in a family of basket makers. He apprenticed in the cloth trade. To make his lenses, he had to learn to grind and polish glass. To make the devices to hold the lenses, he had to learn blacksmithing.
The inventory of Leeuwenhoek's daughter's estate has a section of things that belonged to her father. Among them is a table with a bellows (een tafel met een blaasbalk; image on right).
In his will of 1717, he bequeathed some silver objects to his sister Catherine's son. Jan van Leeuwen received a silver pitcher with some gilded parts, as well as two silver candle holders that Leeuwenhoek made from silver that he worked out of the raw mineral himself:
... een silver schenktaljoor sijnde ten delen verguld, alsmede twee silveren kandelaaren bij den heer testateur gedaan maaken van het silver, dat door hem selffs uyt minerael is gearbeyt.
In his letter of January 12, 1689 (AV/CL 113) addressed to the Royal Society, he wrote:
I have said heretofore how I composed my instruments, which some people would have made far finer and more accurate. But one should know that I have not been trained in any crafts in which one uses a hammer or a file; I have only seen how steel is hardened and tempered, and how a drill is made with which a hole is bored in iron, brass or silver. How and with what a Silversmith solders his silver together.
Having seen this, I have so far trained myself that I have for many years made the tools that I needed for several matters. And that is why what I required for my use was only made a bit roughly by myself.
In the letter of June 9, 1699 (AB/CL 200) also addressed to the Royal Society, he wrote:
While I am writing this letter, I have 8 or 10 magnifying glasses lying about, which have been mounted in silver by me; and although I never received any instruction in working in any metal with a hammer or a file, still I mount my glasses, and my tools have been fitted in such a way that master goldsmiths say that they cannot emulate me.
At the time, Delft had a guild for goldsmiths and silversmiths. In addition, St. Eloy's Gilde organized the blacksmiths, coppersmiths, tinsmiths, and those who made metal locks, boxes and knives. Even if he didn't have any proper "instruction", Leeuwenhoek had many possible models and mentors to watch and learn from.
Leeuwenhoek's letters occasionally mention his working methods. In various letters, writes about anvils, hammering, and filing. In the letter of January 12, 1689, he wrote (my emphasis):
I took a piece of brass, which is about half as thick as the back of a Knife. I beat this brass on an anvil for some time, so it might be stiff, and I then gave it the shape of fig. 2. ABCDEF. After this I made the two big holes GHI. and KLM. in it. In addition I drilled six small holes in it, as PQRS. and NO.
I further beat the part ABF. of this flat piece of brass along the dotted line BF. up in such a way that it formed a right angle at that point, and I did the same with the part CDE.
I furthermore prepared a flat piece of brass of the same thickness, and which I also had beaten hard on an anvil, so that it would be stiff, and could serve as a spring.