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From the first attempts to create a [[fountain pen]], originating in the mid-1800s, the most critical point was to effectively ensure a uniform flow, which would allow the ink to escape from the tank in controlled quantities, which was sufficient to write on a sheet, but not to stain the pockets or the sheet itself. For this purpose the most complex mechanisms of valves, vents, taps etc. were invented, but the solution was not reached until the end of 1800, when it was understood that it was necessary to rely on the phenomenon of capillarity (one of the consequences of surface tension) in order to solve the problem.

From the first attempts to create a [[fountain pen]], originating in the mid-1800s, the most critical point was to effectively ensure a uniform flow, which would allow the ink to escape from the tank in controlled quantities, which was sufficient to write on a sheet, but not to stain the pockets or the sheet itself. For this purpose the most complex mechanisms of valves, vents, taps etc. were invented, but the solution was not reached until the end of 1800, when it was understood that it was necessary to rely on the phenomenon of capillarity (one of the consequences of surface tension) in order to solve the problem.

Il concetto di base su cui da allora cui si basa una stilografica è quello di un serbatoio da cui l'inchiostro può fuoriuscire soltanto attraverso una piccolissima apertura. Questa deve essere sufficientemente piccola da impedire che, per effetto della combinazione della tensione superficiale e della pressione atmosferica, l'inchiostro possa fuoriuscire spontaneamente. Entrambe le forze sono necessarie, come si sarà accorto chiunque si sia ritrovato con la penna che gocciola in presenza di fessure nel serbatoio o di una cattiva tenuta di un [[caricamento|sistema di caricamento]].

The basic concept on which a fountain pen is based since then is that of a tank from which the ink can only escape through a very small opening. The opening must be small enough to prevent the ink from escaping spontaneously due to the combination of surface tension and atmospheric pressure. Both forces are necessary, as anyone who has found themselves with the pen dripping in the presence of cracks in the tank or a poor seal of a [[filling system]] will have noticed.

[[Image:Waterman-52-BCHR-Nib.jpg|thumb|left|Visione ravvicinata del pennino di una [[Waterman 52]] ]]

[[Image:Waterman-52-BCHR-Nib.jpg|thumb|left|Visione ravvicinata del pennino di una [[Waterman 52]] ]]