Since 1960 Museum Boerhaave sells copies of the Van Leeuwenhoek microscopes. These microscopes were made by mr. Arie de Vink, previous restorer/conservator of the museum.
After his retirement mr. De Vink continued with the production. Just recently, on 86 years of age he decided to stop producing them. Understandable, but a problem for Museum Boerhaave. This because there is a regular demand for these copies of the Van Leeuwenhoek microscope.
I was asked if it would be possible to take over the production of these microscopes, which I took on with great enthusiasm. To create a difference between the replica of mr. De Vink’s and mine, I decided to choose an other model of the microscopes in our collection to replicate.
Museum Boerhaave owns five Van Leeuwenhoek microscopes. I choose for the microscope with the convex shape in the plates, to fit the lens in. This choice has some advantages: Because the lens which is used for the replica, has a thickness of2,3 millimetres, it can be easily placed in the concave shapes in the plates. Besides this the microscope is a bit larger in size than the one made by mr. De Vink.
His lens which was placed in the replica made wasn’t functioning for the full 100%. This because of the spherical lens. The disadvantage of this type of lens is that the focal distance is only tenths of millimetres separated from the surface of the lens. If you want to be able to see something through the spherical lens with a diameter of2,5 mm, you’ll have to put the specimen that close to the lens that it will be touching the surface. Tiemen Cocquyt, scientific co-operator of Museum Boerhaave came with the solution! A cut lens, often used in the mobile-phone industry. The main advantage is the focal distance. These lenses (meant for the camera function on your mobile) have a focal distance of about3 millimetres, Therefore it magnifies up to around eighty times. This resembles quite well with the original Van Leeuwenhoek microscopes. Though there were some higher and lower magnifications, but the overall average was around this value.
(Notice: The three microscopes in the boerhaave collection with lens: 74x, 80x and 118x, Two microscopes have no lens.)
Obviously this lens is of modern make, still the lens owns the same capabilities: Standard optical glass, uncoated and the right shape (biconvex)
The lenses in the replica are made in a factory but are just as imperfect as the lenses of the Van Leeuwenhoek microscope. Therefore the lenses used in the replica microscope are the best choice even though there are minor differences. An other advantage of these lenses is that continuity in production is guaranteed, for later orders.
An other problem for the continuity in the production of the microscopes is the making of the screw thread. Van Leeuwenhoek had a screw thread with a pitch of0,8 millimetreon a diameter of2,2 millimetre. This isn’t a standard pitch. On the replica of mr. De Vink’s taps and dies were used which were made by hand. The disadvantage of the use of these taps and dies is that they are very hard work to produce. This also means that there is a high risk of breaking the taps, which means it’s making the production very time consuming and expensive. That’s why I choose to use the coarsest thread still available: 3/32 BSW (British Standard Whitworth 2.3 mmdiameter) which aligns with the original diameter used in the original microscope (2.2mm). The Pitch is finer though, but tests have proven that only real experts will see the difference.
The long threaded arbour which moves the dressingholder up and down has a bit of clearance. This gave a problem, because the dressingholder isn’t fixed to the main plate. By observing the original microscope and the replica made by de Vink, it showed that the squarely bent mounting was bent a bit further, to take away the clearance. This I also applied.
Like the originals the replicas are made out of brass.
The original microscope is coloured dark over the years. To make the replicas match as close to the originals I patinated them without putting on a coating for protection. To allow them to make a patinated surface over the years.
To sell the replica’s as originals is impossible. Therefore the replicas are marked with the Boerhaave logo and have, as been said a different type of screw thread. Also by recalculating the lens, you can tell a modern lens was used.
The result is a hand made replica with a good working lens, which in appearance comes very close to the original microscopes by Van Leeuwenhoek. These replica’s are momentarily only available at Museum Boerhaave for €195,- . For information please contact Annelore Scholten.
Instrumentmaker and Head Conservator of the conservation department of Museum Boerhaave