Commissioned by the University of Padua, the research team ArtesMechanicae has created a replica of the compound microscope by Eustachio Divini, built, as engraved on the brass tripod, in 1672. The original instrument, today the only known existing microscope of this type, is part of the collection of the Physics' History Museum of the University of Padua. A similar specimen was shown at the Royal Society and reviewed in Philosophycal Transaction in 1668.

It is a very singular instrument: its’ telescopic body is composed by four sliding cylinders, the lower one presenting a screw to allow the height adjustment of the whole instrument. The same lower tube supports the objective. This instrument is the only one of this size constructed by Divini: completely extended it has a length of about 50 cm. The lenses are no longer there, so the replica, in a philological perspective, was limited to the body of the instrument and the external decorations.

Two basic choices were made. The first was to not reproduce the instrument with the characteristic signs of wear and aging in order to achieve a true replica in every detail but clearly distinguished from the original.

The second choice was to realize the internal structure not with cardboard, as the original, but by using a resin molded into cylindrical shapes through a rapid prototyping process. Employing a material not known in the seventeenth century allows too to clearly identify the microscope as a replica. Furthermore, the sintered material has the advantage of better mechanical characteristics, allowing at the same time a dimensional control close to a hundredth of a millimeter.

Moving from these premises, the focus shifted to the external parts, in the effort to reproduce them with philological accuracy.

A detailed photographic survey of the outer surface was made, aimed at the reconstruction of the decorations’ textures. From that a first 3D model of the instrument was made through the "123D Catch" software by Autodesk. The model was then refined through a precise dimensional survey.

 

Analysis of materials and finishes:

the coating material of the original instrument is parchment. Nevertheless it was decided to proceed using leather, due to the fact that a suitable parchment, flexible enough to be easily rolled up on cylinders of a diameter of less than 10 cm with a stable in time result is not available nowadays.

The final design and the exact layout of decorations were reconstructed through a vector graphics software.

The gold leaf decorations were made by a specialized artisan, who  decided to proceed by hand with a set of cliché. The decorations have been realized on the flat in spite of the fact that an accurate analysis of the original instrument have led to the conviction that at least part of the decoration was made with the coating already applied on the tubes; the decoration in fact continues seamlessly over the junctions.

The wooden parts were made with boxwood, then finished with wax to have final textures as found on the original. The original wooden parts have indeed some very marked artificial grains, maybe realized later; the Divini’s telescopes at Museo Galileo in Florence don’t have such texture, showing instead the natural color of boxwood. An interesting point has been the difficulty to find piece of boxwood with a suitable diameter, almost 90 mm. Trees that big are almost no longer findable in Europe, as it takes a hundred years for a boxwood tree to reach a diameter of about ten centimeters. It was used instead Brazilian boxwood, a softer variety.

The lower tube has on the outside a screw, a leather strip wrapped in a spiral shape; the cardboard and paper female screw is supported by a brass tripod. This adjustment system allows accurate vertical displacements.