Why Don't Fountain Pens Drip Ink When The Nib Is Down?

[tvergho]

I'm a newbie here, and this is my first post, so I apologize if this question is basic/common knowledge.

 

I just got two fountain pens to test out how good fountain pens are, and I'm really happy with both of them, but what I don't understand is why they work the way they do.

 

From my understanding of the anatomy of FPs, ink moves from the reservoir through the feed to the slit in the nib. This deposits the ink on the paper, through a combination of capillary action and gravity. So why is it, when the pen is held nib down, does the ink not flow out through the slit? Why does ink only flow through the slit in the tip of the nib when it is touching paper?

 

When I got my pens, I was nervous about holding them nib down because I assumed that this would cause ink to leak from the pen. But the only way I can get ink to spill from the pen other than when I'm writing is when I shake it vigorously.

 

Thanks!

[_Stormin_]

The ink is held in by vacuum and surface tension. The ink doesn't flow out until capillary action between the pen and the paper draw it out of the nib, and air moving through the breather hole in the nib replaces the ink in the pen.

[Namru]

Did you ever do that thing as a kid with a straw and coke? Where you draw up the coke into the straw and then put your tounge over the end and it magically holds the liquid? Same thing.

[tvergho]

Oh yeah... That makes sense. Thanks!

[Black Spot]

Magic.

[tvergho]

So it seems.

[GTVi]

Inks contain a "wetting agent" (google it) whose adhesive forces (force between the ink and the nib) are greater than its cohesive forces (the force for the ink to from into a drop). It will adhere to the nib until it is applied to the paper in which case the capillary forces overcome other forces.

 

The straw scenario above is what controls the flow. Hence why the nib has a breather hole

Edited October 8, 2014 by GTVi

[Ron Z]

Hence why the nib has a breather hole

But not all pens have a breather hole. There are a number of modern Waterman models that don't, the Sheaffer "Dolphin" nose Imperials don't, neither does a Parker 75, or 65 nib. I'm sure that folks can come up with many others.

 

The so called "breather hole" is there to prevent a crack from forming at the end of the slit, though I will admit that air does enter the pen through the hole when present. It is possible for air to get into the feed and then into the sac through other routes.

 

A fountain pen is a controlled leak. As ink is drawn out of the pen, air passes back into sac/converter/barrel. On vintage pens if the air channel is cut too deep a pen will drip or ooze ink. The same is true if there is a small leak, say a pinhole, that allows more air into the pen than should be.

[Ernst Bitterman]

I've got a whole page about pen physics that isn't too badly flawed. From it, I lift this instructive diagram.

 

http://dirck.delint.ca/beta/wp-content/uploads/2011/05/drawflow.jpg

[Dinasaurus]

Also, worth noting that the ink stays in the pen for the most part; but if you were to, say, shake it... nib down...with the cap off...there is a chance that you'd have a mess on your hands. I don't recommend trying!

[Icywolfe]

If you add a good bit of Photoflo or dish washing soap in your ink. The ink will just flow out like a river. Those prevents surface tension. It's surfance tension that keeps ink in your pens. And some fairy dust and maybe some mad wizard magic.

[GTVi]

But not all pens have a breather hole. There are a number of modern Waterman models that don't, the Sheaffer "Dolphin" nose Imperials don't, neither does a Parker 75, or 65 nib. I'm sure that folks can come up with many others.

 

The so called "breather hole" is there to prevent a crack from forming at the end of the slit, though I will admit that air does enter the pen through the hole when present. It is possible for air to get into the feed and then into the sac through other routes.

 

A fountain pen is a controlled leak. As ink is drawn out of the pen, air passes back into sac/converter/barrel. On vintage pens if the air channel is cut too deep a pen will drip or ooze ink. The same is true if there is a small leak, say a pinhole, that allows more air into the pen than should be.

I suggest you grab yourself a demostrator, fill it with water, and let the nib soak in a tissue, then you will see the air bubbles flow back into the converter as the water soaks out. Then you will see the pen "breathe". Its not rocket science.

 

I fell on the floor laughing of your term "controlled leak". That's an oxymoron, A leak by definition is not by design therefore is not controlled. But I understand what you meant...its a well designed flow based on the properties of the ink and nature. A pen in ideal condition and atmospheric condition will not leak. But it will dry out eventually. Would you not expect that to be the case?

Edited October 8, 2014 by GTVi

[amberleadavis]

I've got a whole page about pen physics that isn't too badly flawed. From it, I lift this instructive diagram.

 

http://dirck.delint.ca/beta/wp-content/uploads/2011/05/drawflow.jpg

 

Ernst, this image came up on Google when I was doing a search, great explanation!

[______Zaphod_Beeblebrox]

To bad Calvin and Hobbes never covered this subject because then you would have the definitive answer!

[amberleadavis]

LOL Good point.

[amberleadavis]

Here is a set of researchers explaining why pens write,

 

http://phys.org/news/2011-12-deconstruct-physics-fountain-pen.html