Traditionally the artist first makes a big model for the coin in clay or wax, of which a plaster model is cast. A so called pantograph then `feels` the plaster model and engraves the diminished design into the stamp.
Today most designs are computer made, to be milled into the steel in one go. For complex designs it is better however to mill several layers into large templates first. As with plaster casts these templates are engraved into the steel with a pantograph. In our case this was done with the background patterns in the border text `ARS PECUNIAE MAGISTRA`. In this background the 3D model can be milled layer by layer.
The stamp is negative – so left will be right and the deeper the cut, the higher the coin. The art is of course to create a real 3D effect in a depth of only 0.3 mm. Depending on the design, but for a major part also on the engraver. He or she has to estimate how deep which part of the design will be.
After the computer executed milling work the image is engraved in the steel, however all the paths of the milling machine are still visible. The engraver has to eliminate them by hand with precision instruments. This really acquires the hand of the master who at the same time applies the details.
Master engraver Lei Lennaerts of Venrooy Goud- en Zilverindustrie did the engraving on the coin side of our currency. This will be the standard ‘backside` - the other side will be designed by alternating artists. In the cartouche between the two flying wheels of the press there is room for a unique series and piece number for every coin.
Next the steel stamp has to be hardened, meaning: heated to a temperature of about 770 degrees Celsius and then quickly cooled in oil. This changes its internal cristal structure and makes the steel diehard. As this process makes the steel brittle at the same time, it is once more heated but to a lower temperature than before and cooled very gradually. Only then the stamp is hard as wel as durable and can be used to mint coins.
More information about engraving see Lei Lennaerts` website.
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