How To Prevent An Eyedropper From Leaking Into Cap?

January 12, 2015

So I did a silly thing: I sprung the nib on Pilot Falcon. Fortunately I was able to remove it an repair it. The bad news is I pushed nib out from the back and inadvertently wrecked the little plastic bit where the c/c fits in. I have been using it as an eyedropper and it works great when it's full. Once the ink level drops a bit putting on the cap causes the pen to discharge ink. I have tried putting the cap on with the pen point up and I get the same result whenever the position of the pen changes. I have tested it loads of times and the source of the leak most certainly stems from the action of putting on the cap. Is there anyway to prevent this? I quite like the pen as an eyedropper, as I was let down by the low capacity of the converter. However, having a capful of ink once the pen runs a little low isn't terribly convenient. Is there anything I can do other than be super careful to never let the nib face anywhere close to downwards?

January 13, 2015

So I did a silly thing: I sprung the nib on Pilot Falcon. Fortunately I was able to remove it an repair it. The bad news is I pushed nib out from the back and inadvertently wrecked the little plastic bit where the c/c fits in. I have been using it as an eyedropper and it works great when it's full. Once the ink level drops a bit putting on the cap causes the pen to discharge ink. I have tried putting the cap on with the pen point up and I get the same result whenever the position of the pen changes. I have tested it loads of times and the source of the leak most certainly stems from the action of putting on the cap. Is there anyway to prevent this? I quite like the pen as an eyedropper, as I was let down by the low capacity of the converter. However, having a capful of ink once the pen runs a little low isn't terribly convenient. Is there anything I can do other than be super careful to never let the nib face anywhere close to downwards?

I think you need to seal some of the threads up with silicon grease, the reason for ink to start to run out of a nib is if the chamber is filling with air and forcing ink out of the nib and or feed.

January 14, 2015

Seems to me that a fountain pen depends on the vacuum at the rear of the pen barrel

to hold the column of ink from rushing into the feed. The volume of ink in a cartridge

or converter is relatively small, compared to the large, heavy column of ink in the entire

pen barrel.

So, if the column of ink is too heavy for the vacuum, some ink "burps" out. If the air

leakage compromises the vacuum, some ink "burps" out.

Remember >> Your pen was not designed as an "eyedropper" fill pen. You altered the

pen, without the applied engineering knowledge, and without consulting the pen designer.

Eyes open ! Go for it ! Have fun ! Don't do it on the wife's new carpet.

January 15, 2015

I think you need to seal some of the threads up with silicon grease, the reason for ink to start to run out of a nib is if the chamber is filling with air and forcing ink out of the nib and or feed.

I have sealed the the threads with silicon grease. It doesn't seem to leak or burp during normal usage, just during the act of capping.

January 16, 2015

Seems to me that a fountain pen depends on the vacuum at the rear of the pen barrel
to hold the column of ink from rushing into the feed. The volume of ink in a cartridge
or converter is relatively small, compared to the large, heavy column of ink in the entire
pen barrel.

So, if the column of ink is too heavy for the vacuum, some ink "burps" out. If the air
leakage compromises the vacuum, some ink "burps" out.

Remember >> Your pen was not designed as an "eyedropper" fill pen. You altered the
pen, without the applied engineering knowledge, and without consulting the pen designer.
Eyes open ! Go for it ! Have fun ! Don't do it on the wife's new carpet.

I am a single university student with no carpet in my apartment, so that is one worry I don't have. It seems the act of capping the pen must be creating some kind of vacuum which draws the ink out. The pen never leaks during usage, only when the cap is put on and only once the ink level drops below full.

January 17, 2015

The relatively large ink/air volumes found in eyedroppers can create a vacuum during (un)capping causing the annoying effect you observed. The problem is traditionally solved by eyedropper manufacturers by drilling a (small, about 1 mm diameter) ) cap breather hole for rapid pressure equalization during (un)capping. Those pressure equalization holes are positioned just under the cap seal.

Edited January 17, 2015 by Fuellerfuehrerschein

January 20, 2015

The relatively large ink/air volumes found in eyedroppers can create a vacuum during (un)capping causing the annoying effect you observed. The problem is traditionally solved by eyedropper manufacturers by drilling a (small, about 1 mm diameter) ) cap breather hole for rapid pressure equalization during (un)capping. Those pressure equalization holes are positioned just under the cap seal.

I noticed my Vacumatic had a hole in the cap. I always wondered what it was for. Before I attempt any surgery on my cap, where exactly should I drill this hole? I assume it goes below the nib/feed section when the cap is placed on the pen. That appears to be where it is located on my Vacumatic.

January 20, 2015

Traditional eyedroppers have their cap breather holes positioned at about the middle of the grip section when the pen is fully capped so that when the pen is capped, the inner cap will seal the nib, thus preventing dryout. I just realized the Pilot Falcon uses fine threads to close the pen. Traditional eyedroppers feature similar fine threads to positively close these pens.

Edited January 20, 2015 by Fuellerfuehrerschein