Burping In Eyedroppers Or Piston Fillers

[bobje]

I think I understand why eyedropper-filled pens burp. At about 1/3 full, the air inside the eyedropper chamber expands and forces out some ink.

 

But why doesn't this occur with a piston filler?

[jar]

Usually there is a layer of insulating air between the internal and external chambers in a piston pen.

[Fuellerfuehrerschein]

A simple traditional ebonite feed must work hard to control the ink flow during significant temperature rises in the ink/air column in an almost empty 3 to 5 ml eye dropper barrel. The heat of the user’s hand causes the trapped air column to expand, pushing the ink contained under the air out. During winter, I must keep my Indian ebonite eye dropper half full for optimal function. I encounter increased ink flow (a wetter line) as a warning sign when my pen gets low on ink. Burping only occurs when I refuse to top up the ink.

 

Modern fountain pens have heavily finned feeds for buffering more ink and even piston fillers seldom have more than 1.5 to 2 ml ink capacity to control and minimize air expansion problems.

 

See https://www.fountainpennetwork.com/forum/topic/256177-pelikan-piston-filler-ink-capacities/ and https://www.fountainpennetwork.com/forum/topic/182350-ink-capacities/ for the ink capacities for some pens.

[Mech-for-i]

I've been hearing this ink burping problem for ages, but for one who had used eyedropper and piston filler for decades I've never had this problem, even when ink level was somewhat low. I put it down to the kind of pen I had and the way I hold my pen. First of all I have a man size S hand, but actually I got a rather small palm and consequently long fingers. I tend not to grip the pen but cradle it. I suppose in this pose I never got the chance to actually heat up the pen enough to give the problem a chance. The other part being how good the feed actually feeds, that is feeding air and ink interchange.

 

That said I've heard enough stories about people using Pelikan and TWSBI having their pen burping ink so I guess Piston filler is not immune to that. Nor do some C/C though I doubt it had to do with the particular hand warming up the pen part.

[rwilsonedn]

it does occur in older (or cheaper) piston fillers with simple feeds. Also in syringe and bulb fillers, and even, under extreme circumstances, in cartridge or converter pens. No pen can perfectly insulate the air inside whatever reservoir it uses from changes in the temperature of the barrel. The question is whether the feed has enough capacity to capture any ink that gets trapped between the expanding air in the reservoir and the nib.

ron

[Connly33]

I did have this issue with my piston filling TWSBI Eco Fine untill i sent it in and they put a dryer feed unit in the pen, and i haven't had the issue since. So as others have said i think the feed plays a big role in controlling this. With wetter writing inks especcialy this was an issue for me.

[Bo Bo Olson]

I've never had any problems with vintage and semi-vintage German piston pens burping. Never even read that before.

Can be wrong.... but I am not going to suddenly start worrying my cool weather German pens are going to go on strike demanding AC.

[A Smug Dill]

Even cartridge/converter-filled pens can burp, and not from any defect in construction or assembly.

 

I've been blasé about where I leave my newish Sailor Profit Casual pen, in which I've installed a converter — filled with ‘Guitar’ Modern Red ink, which I haven't found to be an ink that is prone to nib creep.

 

Lately, when unused, the pen tends to lie horizontally on the half-dead keyboard of my old MacBook, since I now have to type on an external keyboard to use the machine; but that ‘platform’, with all the island-style keys that so conveniently work as roll-stoppers, can get pretty warm. The cap of the pen is usually near where the Esc key is, and so the barrel is closer to where the heat source is.

 

Twice this week now I've uncapped the pen to find the nib covered with globs of liquid red ink, and there are also droplets inside the translucent inner cap. I cleaned the mess up the first time, but it happened again.

 

Apart from the obvious, “Don't do that, then!” or that burping is unlikely to happen from the warmth of the user's hand alone while writing, the design of the pen or filling mechanism itself does not have any inherent safeguards or suppression against burping as a phenomenon.