- #1
physicsisphirst
- 233
- 3
this is a unique fountain pen from the 60s in that you don't squeeze anything to get ink into it. you just dip the solid one piece 'cartridge' into the ink and it fills, presumably through capillary action - i don't know what's inside, but i doubt if it is a sponge to have lasted all these years.
now if i keep the pen rightside up (the way you'd carry it on the clip in your pocket), i can write with it immediately. if i keep it upside down, no ink makes it to the nib despite the seeming gravitational advantage.
if the instrument works on capillary action, the meniscus needs to be concave up in order for the surface tension to cause the ink to flow upwards against gravity. if we turn the pen downwards, the same capillary action will presumably cause the ink to go in the other direction despite gravity.
the only difficulty I'm having with the above reasoning is that when upsidedown
1. the ink doesn't flow out of the other end or flow to the nib
2. the full-weight of the ink is towards the nib, but doesn't make any progress to it
what I'm wondering is whether when upsidedown, the shape of the meniscus is sufficiently altered at both ends (though i don't know if it is correct to call it a meniscus at the bottom) so that capillary action stops completely.
if so, this would seem to suggest an asymmetry in the capillary tubes perhaps (may be they narrow with proximity to the nib?), so that ink goes only one way?
ideas or explanations?
in friendship,
prad
now if i keep the pen rightside up (the way you'd carry it on the clip in your pocket), i can write with it immediately. if i keep it upside down, no ink makes it to the nib despite the seeming gravitational advantage.
if the instrument works on capillary action, the meniscus needs to be concave up in order for the surface tension to cause the ink to flow upwards against gravity. if we turn the pen downwards, the same capillary action will presumably cause the ink to go in the other direction despite gravity.
the only difficulty I'm having with the above reasoning is that when upsidedown
1. the ink doesn't flow out of the other end or flow to the nib
2. the full-weight of the ink is towards the nib, but doesn't make any progress to it
what I'm wondering is whether when upsidedown, the shape of the meniscus is sufficiently altered at both ends (though i don't know if it is correct to call it a meniscus at the bottom) so that capillary action stops completely.
if so, this would seem to suggest an asymmetry in the capillary tubes perhaps (may be they narrow with proximity to the nib?), so that ink goes only one way?
ideas or explanations?
in friendship,
prad