# Why does a fountain pen soak ink automatically at times?

I've had a rather interesting fascination with fountain pens. The mechanism is a thing of beauty, but my attention was recently caught by a rather insignificant phenomenon which I've used a lot in my experience with them. That of soaking leftover ink. All the bright folks here who've written with one must know that a fountain pen soaks ink at times(I do this with the leftover ink in the pot cap to dry it up), and this happens till a certain amount has entered the nib(it varies, of course with the tank airspace and possibly other parameters)

I've looked up how a fountain pen works, and to the best of my knowledge, I couldn't find a clear mechanism which shows why this happens.

I have a vague idea of how it could work:

The four chambers in the jib/nib are built for ink($$I_1, I_2 \& I_3$$)/air($$A_1$$) exchange. $$A_1$$ replenishes the vacuum that would have otherwise formed while the tank got devoid of ink while writing(here $$A_1$$ does not fill up with ink). Now when I'm soaking some up through $$I_1, I_2 \& I_3$$, there is no place for air to enter $$A_1$$ and somehow ink goes up through $$A_1$$ too alongside $$I_1, I_2 \& I_3$$(or it opposes the flow). Now, this is where it's all fuzzy for me, assuming what I've put forward is logically true. What phenomenon could cause ink to be pushed through $$A_1$$?

Is it possibly a minute pressure difference between the tank and where the end of the nib(aka the capillary) is placed, that causes this unprompted flow?

Some clearing up will be appreciated. Thank you:)

• To clarify, you are asking how the ink gets into a dry fountain pen? – QuIcKmAtHs Nov 15 '18 at 13:01
• You could say that, though I've seen this happen with partially or completely(with some air bubbles obviously) filled tank and a wet nib. – Abhinav Nov 15 '18 at 16:39
• Im sorry, but im still confused. what exactly is your query? – QuIcKmAtHs Nov 16 '18 at 11:50