Why does ink flow towards the nib of a disposable pen, but does not flow out of the open end of the plastic tube when it is left horizontal?
In: Engineering
It’s a combination of a vacuum and surface tension. If the ink were to flow out the end of the tube, there will need for there to fill the gap with air or something else. The surface tension of the ink helps prevent air from making it’s way down the tube which helps maintain the lack of air at the nib end. Depending on the viscosity of the ink, some companies cap the ink with another substance to ensure that the ink doesn’t flow out.
As for how I figured this out, I stuck a needle down the tube of a disposable pen in the past and some of the ink flowed out.
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