Inexpensive eyedropper pens...?

[A Smug Dill]

26 minutes ago, AceNinja said:

If the oring is sitting at the barrel end face, not only it does not seals the ink (due to the none flat barrel end face),

 

That is actually incorrect. O-rings are made of rubber that will yield under pressure, and subject to being deformed so it would mould itself to any irregularities on the surfaces pressed against it, thus providing that perfect seal, in spite of being solid instead of fluid/liquid matter.

 

[dipper]

1 hour ago, AceNinja said:

*note that I've never eye droppered a preppy, or any other pen.  Just my gut feeling.

I understand your gut feeling.

 

But actual experience with Preppies reveals that getting an o-ring to sit inside the barrel requires an exceptionally thin cross-section width o-ring. I have attempted to create such a super thin ring from self-amalgamating rubber tape, cut to 0.5mm width and 60mm length, then stretched to wrap around the pen grip-section. (It goes round about ten times if you use the whole piece.) I could not make the ring thin and uniform and robust all at the same time.

If anybody knows of a supplier of super-thin o-rings that would be interesting.

 

Thread sealing with grease? That makes sense with a close fitting well engineered thread - as some pens do have. The Preppy has loosely mating threads, and one female double-start thread is omitted from the barrel thread molding.

 

My Preppy, sealed with a trace of silicone grease on the flat(ish) barrel end alone is still not leaking.

 

[Arkanabar]

Unless shipping is cost-prohibitive, you might try fprevolutionusa.com, peytonstreetpens.com, or ASApen.in.  All carry a variety of eyedropper-filled Indian pens. 

[Arkanabar]

I should add that, as you live in the UK, you might want to beware of Charles' Law, and its effect on air volumes and pressures in large ink chambers.  (See "burping": 

 

[dipper]

Here is the conclusion of my one (and only one 🤣😂🤣) test of a Preppy, eyedropper filled, without any o-ring. Just a light smear of silicone grease on the threads and the end face of the pen barrel.....

 

Until the very last day the pen was a joy to use. Consistent ink flow, slightly wetter than when using a cartridge, looks cool with all the ink sloshing around inside the crystal clear body.

Boxing day, the pen was nearly empty. Large air volume inside. Moving between cold areas of the house and then sitting in front of a wood-burning stove. Burping expected! But no, the Preppie's feed-of-many-fins handled the air expansion without burps.

 

But ..... It finally leaked!

 

Next day the pen ran dry. (There was still some ink inside, but that ink could not reach the nib. The tall post at the back of the grip-section, intended to be pushed through the neck of an ink cartridge, prevents the last drops of ink from reaching the nib.)

Ink started seeping very slowly from the barrel/grip-section joint. My right hand became spectacularly stained blue before I noticed what was happening.

 

The pen still looks perfect. My right hand does not.

 

So what to do? ........

 

Grind off the slight raised areas at the end face of the barrel? ... Result will certainly look and feel smooth, but needs to be perfectly flat and perpendicular to the pen axis. Too difficult.

 

Refill pen before completely empty? ..... Maybe? But not logical. There is no excess pressure inside a burping eyedropper. Burping is due to excess volume. Pressure does not increase to "force" ink out at the screw joint, because the front end of the nib/feed is open to atmosphere. Increase in temperature at constant pressure causes increase in volume - Charles' Law.

 

Don't use the pen so much? If stood in a pen cup on a desk and used only occasionally, then possibly any slight seepage may dry in the pen screw joint, self sealing any tiny gaps? I note that matches the description of use given by @A Smug Dill earlier in this topic.

 

Slather on a thick coating of silicone grease, filling the thread spaces entirely? OK if the grease stayed put. I predict a greasy mess though.

 

Revert to refilling Platinum cartridges? Yep, I think so..... 😣.

 

Or..... buy a pen designed to be eyedropper filled!

Thanks to this topic there are many options given in earlier posts for "economical eyedropper" pens. I am very much tempted to get one.

[Karmachanic]

On 12/10/2022 at 9:49 PM, smol_medic_hope said:

The Opus 88 has caught my eye, but, uh, budget

 

Take a look at the Majohn C4.  Complete with shut-off valve.  3.8ml capacity. £25

[MuddyWaters]

On 12/29/2022 at 8:50 AM, dipper said:

Here is the conclusion of my one (and only one 🤣😂🤣) test of a Preppy, eyedropper filled, without any o-ring. Just a light smear of silicone grease on the threads and the end face of the pen barrel.....

 

Until the very last day the pen was a joy to use. Consistent ink flow, slightly wetter than when using a cartridge, looks cool with all the ink sloshing around inside the crystal clear body.

Boxing day, the pen was nearly empty. Large air volume inside. Moving between cold areas of the house and then sitting in front of a wood-burning stove. Burping expected! But no, the Preppie's feed-of-many-fins handled the air expansion without burps.

 

But ..... It finally leaked!

 

Next day the pen ran dry. (There was still some ink inside, but that ink could not reach the nib. The tall post at the back of the grip-section, intended to be pushed through the neck of an ink cartridge, prevents the last drops of ink from reaching the nib.)

Ink started seeping very slowly from the barrel/grip-section joint. My right hand became spectacularly stained blue before I noticed what was happening.

 

The pen still looks perfect. My right hand does not.

 

So what to do? ........

 

Grind off the slight raised areas at the end face of the barrel? ... Result will certainly look and feel smooth, but needs to be perfectly flat and perpendicular to the pen axis. Too difficult.

 

Refill pen before completely empty? ..... Maybe? But not logical. There is no excess pressure inside a burping eyedropper. Burping is due to excess volume. Pressure does not increase to "force" ink out at the screw joint, because the front end of the nib/feed is open to atmosphere. Increase in temperature at constant pressure causes increase in volume - Charles' Law.

 

Don't use the pen so much? If stood in a pen cup on a desk and used only occasionally, then possibly any slight seepage may dry in the pen screw joint, self sealing any tiny gaps? I note that matches the description of use given by @A Smug Dill earlier in this topic.

 

Slather on a thick coating of silicone grease, filling the thread spaces entirely? OK if the grease stayed put. I predict a greasy mess though.

 

Revert to refilling Platinum cartridges? Yep, I think so..... 😣.

 

Or..... buy a pen designed to be eyedropper filled!

Thanks to this topic there are many options given in earlier posts for "economical eyedropper" pens. I am very much tempted to get one.

 

Really good post. Thanks for sharing!

 

Can you explain the bolded part a bit more? You are saying that refilling the pen barrel to the max would not have prevented the leakage through the section-barrel joint? 

 

Otherwise, nice to hear how solid the Preppy was. 

[dipper]

12 hours ago, MuddyWaters said:

Can you explain the bolded part a bit more?

(The part, bolded by @MuddyWaters, was my assessment of why the Preppy leaked on the final day of its test.)

 

Glad to explain.....

 

Every fountain pen has to deal with temperature changes.

We might imagine that a fountain pen copes with those chages by "holding in" all the air and ink inside the pen, by "resisting" the forces of evil! .... But that would be a misunderstanding.

 

(There are in fact a few pens that do "hold in" their ink and air, to prevent leaks. Those are pens that include a mechanism that seals off the ink chamber when not in use. Perhaps by turning or depressing a knob at the rear of the body. To use one of those pens to write you turn or pull out the knob, to open the seal. Then shut off the pressure seal after use.)

 

Most pens do not have such a feature. The nib/feed end of the pen is open to the atmosphere - permanently. But despite being exposed to the atmosphere, ink does not fall out of the nib end of a pen. That is due to a combination of ink surface tension effects, and the narrow size of the channels linking the main ink chamber to the outside world.

 

The result is that when the temperature changes, the volume of the air inside the pen goes up or down whilst staying very close to the external air pressure. That behaviour is exactly what the ink/air exchange channels in a pen feed are designed to do.

 

There is an undesirable, but unavoidable, side effect when the air inside the pen's ink chamber changes its volume. If that change is an air expansion and the pen is being held nib down, then some ink will move ahead of the expanding air, out into the nib and feed, and potentially flood the feed and become a "burp". There is nothing preventing the ink moving through the channels in the feed in this way. (They are the same channels that the ink flows through, quite freely, when you fill a fountain pen from a bottle.) Though we like to say "The air forces the ink out of the pen", that is misleading. There is no significant "force" involved.

 

The air space gets a bit bigger, and the ink moves with it, in the same way that when you slowly raise or lower you arm then your hand moves up or down with it!

 

Fountain pens generally deal with these small quantities of excess ink by hanging onto the excess ink in the side-fin-slits and in other crevices and crannies around the edges of the feed. So we do not see burping except in extreem circumstances.

 

Unfortunately for users of pens with an extra-large ink capacity, a large ink capacity also means a large air volume inside when the pen in nearly empty of ink. That difference does not make the air rise to a greater pressure when the pen warms up in the users hand. (Remember the ink/air chamber is open to the atmosphere, as explained above.) The larger air volume simply means there is more air doing the expanding - and that volume increase all moves the ink, ahead of that expansion, out of the ink chamber and into the feed.

 

So when my Preppy was nearly empty I did not predict any greater pressure changes inside the pen. What I did expect was greater volumes of excess ink to move into the feed whenever the pen was warmed. So I was on the lookout for burping.

In fact the Preppy feed, visible inside the transparent grip section, coped easily with all excess ink flow. It does have a spectacular number of narrow and deep side slits.

 

Restated in scientific jargon, "Charles Law" states that if a fixed mass of gas is held at constant pressure then its volume will change in proportion to the absolute temperature.

 

The explanation above is about why and how the air inside the pen is at constant pressure, and therefore why we can expect burping when a pen is nearly empty, but also why we have no reason to expect ink to be "forced" out of greased joints when the pen is nearly empty.

 

So I am puzzled! The Preppy did slowly seep ink all over my hand, in the final moments before running dry - through a joint that had been good for many days of use up to that point.

[MuddyWaters]

9 hours ago, dipper said:

The explanation above is about why and how the air inside the pen is at constant pressure, and therefore why we can expect burping when a pen is nearly empty, but also why we have no reason to expect ink to be "forced" out of greased joints when the pen is nearly empty.

 

So I am puzzled! The Preppy did slowly seep ink all over my hand, in the final moments before running dry - through a joint that had been good for many days of use up to that point.

 

Thanks for the explanation. That makes a lot of sense. I agree with you but it makes a bit more sense to me to include the concepts of pressure and force (the duelling of the forces inside and outside the container of ink). [After re-reading this post, I think we are saying the same thing.]To use your example, when you lift the arm, the arm applies a force to the joint, which applies a force to the forearm, and then to the wrist joint and then the hand. Likewise, if a certain amount of gas is heated, either its volume or its pressure will increase (PV = nRT). Now, because the pen's ink is open to the outside air and it can freely expand, the volume does effectively increase without much resistance or pressure build up, but in pens where there is more resistance, then the force/pressure required to expand the volume against those external resistances (walls of the barrel, nib unit, feed, ink surface tension of ink in the feed, etc) is greater.

 

Probably in the case of the preppy, there is less resistance for ink to come out through the loose barrel threads than through the very tight feed, which also has ink surface tension in it to hold the stored ink behind the feed and remain in the barrel. This is why in Indian eye dropper pens, the ink just comes out instead through the very loose feed, though also through the threads. But once the pressure reaches a certain point, which means the fixed amount of air, previously held in a fixed volume, rises in temperature, it will need to have its volume expand somewhere where there is a lack of resistance. 

 

Why does it come out when the barrel is nearly empty? I am not sure, maybe a collection of the following: 

-less ink surface tension

-more transfer of heat from the hand directly to the air inside the barrel

-more volume being displaced

-silicone grease degrades over time?

 

I have found silicone grease to not be as good as an o-ring, so pens like the preppy that cannot take an o-ring and have too much spacing between the threads are not too well suited for eyedropper conversion. The Kaweco sport on the other hand was very good, probably because at least the threads are tighter. 

[dipper]

4 hours ago, MuddyWaters said:

.... but in pens where there is more resistance ....

"The resistance" .... hmmm?

Let's dive deeper into that (or feel free to just skip out of our nerdy fun discussion 😃).

 

The change in pressure between the two ends of a straight hollow circular cross section pipe, when a fluid is flowing through the pipe, is given by the Hagen-Poiseuille Equation.

One formulation of that equation is:

DeltaP = 8 x Pi x length of pipe x dynamic viscisity of the fluid x the volume flow rate / the square of the cross-section area of the pipe.

 

Though the flow paths through a feed and nib are neither straight nor circular we can see some useful and relevant aspects of the straight pipe equation.

 

A ) If cross section area is made smaller then the pressure difference becomes greater because area is the divisor in the equation. In fact a lot greater, as the area is squared. That is the aspect noted by @MuddyWaters.

 

B ) Also note that DeltaP is proportional to flow rate. So the pipe (or feed) cannot maintain or hold back any pressure difference unless ink is flowing.

If flow rate = 0 then pressure difference = 0.

"Burp" inkflow can give a brief pressure difference but as soon as the air has expanded, in a time limited only by inertia, the flow rate becomes zero and the pressure difference must also drop to zero. (That is also true with my simplified arm&hand analogy, as pointed out.)

 

I conclude that if a pen is subjected to a very rapid temperature increase, say by hitting it with intense infra-red or dipping it into hot water, then the expansion rate may be sufficiently high for inertia and viscous drag (the H-P eqn) to give a brief pressure increase inside the pen.

That process is in agreement with @MuddyWaters, and is consisten with known physics.

 

My intuition though is that the effect, if present, is going to be small, and very brief.

 

I feel (and agree) that the observed slow seepage leak, continuing over a period of ten or twenty minutes, was more likely to be due to a failure of the silicone grease seal.

If that joint became a narrow capillary gap ...? Oh dear! ... ink will be drawn into the narrow gap by capillary action ... and onto my fingers where I am holding the pen body.

 

- - - - - - - - - 

 

Using the forum search tool to locate this topic, a similar old topic popped up also! ....

 

 

 

[mhguda]

Thanks @MuddyWatersand @dipperthat became a very interesting exercise in physics.

My feeling is that @dipper is on track with the capillary action effect as cause of the leak when the pen was almost empty... I think I've experienced that with some of my, not so inexpensive, Indian eyedropper pens, even when they were almost full of ink... and just lying in their pen tray. And no large temperature differences to trigger anything... I had such things happen when I was playing with inks to which I'd added glitter, in order to play with shimmering inks. It worked, in a way, but in some instances gave unexpected messes...

Anyway, I enjoyed you guys' discussion. So thanks!

[Nellie]

Surprised that no one's mentioned the Majohn C1 (or have I missed it?). No burping from mine so far, even, unlike what the Preppy I used as an eyedropper a decade ago did. Maybe PandaPenclub on YT is right and the C1's thick barrel walls prevent it? In any case it is a demonstrator, aside from its opaque section, and it comes with an eyedropper and o-rings installed.

[A Smug Dill]

4 hours ago, Nellie said:

Surprised that no one's mentioned the Majohn C1 (or have I missed it?).

 

On 12/11/2022 at 9:26 AM, A Smug Dill said:

Majohn makes several pen models designed exclusively to be eyedropper-filled; the M2 as @MuddyWaters mentioned, as well as the S7, C1, Q1, etc.

 

[TitoThePencilPimp]

Kaweco Sport.

[dipper]

7 hours ago, Nellie said:

....... no one's mentioned the Majohn C1 (or have I missed it?). No burping from mine so far, ......

 

My C1 has burped. But that was an extreme test during cold wintertime in the UK, in an old house, moving between unheated rooms and other rooms with woodburning stoves blasting out heat.

 

By coincidence my C1 happens to be the pen I am using today - fitted with a Waterman long international cartridge for safety.

 

I agree that the C1 should be on the list of inexpensive eyedroppers. It works well, is well made, looks good.

 

It is towards the top of the "inexpensive" price range, costing as much as a handful of Preppies.

I found the C1 heavy and uncomfortable to hold at first, but that was over a year ago. Now it feels perfectly OK.

 

The C1 has one unusual feature relevant to burping. To limit the risk of burping it is beneficial to hold an eyedropper nib-upwards. (That is not a guaranteed cure, but is always better than laying the pen horizontal on a tabletop at intervals during a session.)

The C1 pen can stand upright on a tabletop all by itself, without needed a pen cup or similar. It has a wide flat end on both body and cap.

 

When eydropper filled, with half a gallon of ink inside the crystal clear body, the C1 looks spectacular.

[Nellie]

16 hours ago, A Smug Dill said:

 

 

🙈 Sorry! I thought you'd only listed the other Majohns.

 

That sounds great @dipper. I'm really happy with mine too. Looking at it cheers me up while I'm working.

[Katharine]

On 12/29/2022 at 8:50 AM, dipper said:

Or..... buy a pen designed to be eyedropper filled!

Thanks to this topic there are many options given in earlier posts for "economical eyedropper" pens. I am very much tempted to get one.

That would be my choice.  I know some people do it for the fun of engineering an eyedropper pen from one that is not an eyedropper, but I figure by the time I buy and pay shipping for a bunch o-rings and silicone grease I only need a tiny bit of, take the time to fiddle around and put it all together correctly, and possibly pay the price if I mess (literally) it up... I will have spent enough in money and time and hassle to have gotten a decent pen that was designed to be an eyedropper in the first place...  (I guess for me I'd be more aiming to have a pen that works than the interest of the fabrication of same, at least in this case.)

 

I did have a cheap eyedropper once; Indian IIRC.  I liked it, but then I somehow got a crack in the threads and that was the end of that pen.

[amper]

I used Platinum Preppys converted to eyedropper with o-ring and silicone grease for insurance as my primary pens from early 2013 to late 2017. I never once had a single issue with leakage or cracking. Since late 2017, I've used TWSBI ECOs.

One great thing about an eyedropper pen is you always know when it needs more ink, because at some point, the ink starts coming out faster, due to the heat from your hand causing the air in the barrel to expand. When the pen starts writing like it's having a heavy flow day, it's time to refill.

[Ink Stained Wretch]

On 12/29/2022 at 8:50 AM, dipper said:

Revert to refilling Platinum cartridges? Yep, I think so..... 😣.

 

That's what I'd do, but then I would say that 😃. I'm a real advocate of refilling cartridges.