Air pressure is forcing the ink out of the tube.
It starts with pen
needle? The part of a pen that starts with "n" is NIB. The nib is the writing part of the pen.
Thank you so much it helped me for a test
a squid with a leaking pen
pen
PEN
a fountain pen starts leaking at higher altitudes because the difference in air pressure is less than it is on the ground so the ink flows quicker so not exactly a leak rather you not being able to keep up with the flow from the cartridge.
'Nib' is the writing point of a pen.
pentagon
Pensive
O Henry