Tips and Hints

Eyedropper Conversion…

Hi Pen Fans!

Highlights from the video…

1.  What is an eyedropper.
2.  Why make a pen into an eyedropper.
3.  How to convert a cartridge/converter pen to an eyedropper.


Brian at Edison

19 replies on “Eyedropper Conversion…”

Excellent video! I did this for the first time to my Bexley 56 a couple months ago and it’s worked out well. Thinking about also doing it with my Edison Nouveau Premiere and/or Edison Pearl. I didn’t know the part about applying grease to the threads around the nib.


Adding grease to the threads around the nib (housing threads), is not always necessary, but if you are comfortable unscrewing the nib, there’s not harm in doing it.


Hey, Brian – I’m a fountain pen newb, but my understanding of the eyedropper burp is essentially that the warmth of your hand causes the air inside the pen to expand. Eyedroppers are more prone to this, because your hand is in direct contact with the ink reservoir (aka, the barrel) and because there is such room for a mass of air. One would be inclined to think perhaps an eyedropper would be prone to this as well. However, these tend to have a breather tube which can equalize pressure (as well as a flexible sac, which will "give" to the increased air pressure, unlike rigid plastics used in barrels — though I imagine this is not as great a factor).

Hi Josh.

I really don’t think that the burping has anything to do with heat from your hand. If it were heat from your hand, then this would happen at any time – not just when the fill is low. And eyedroppers are only prone to this at the very end of the fill…that last very bit of ink.

Also – if this were due to heat, wouldn’t it be a gradual phenomenon? ED burping occurs quickly.

Someday in the near future, I’m going to do temperature experiments. Ink up a pen, lay it on it’s side, and then go from the fridge to room temperature and vice versa to see what happens, when it happens, and at what temperatures.

I appreciate your feedback, but I lean away from the hand-heat-theory.

I’ll do more homework, but my understanding is that the burp is a result of the pen suddenly losing it’s vacuum. What causes this at the very end of a fill is still a mystery to me.



I did a little more homework on this, and my theories on eyedropper burping was confirmed by some guys that I look up to.

It really has very little to do with heat. If this were the case, any filling system that exchanged air for ink (which is every one) would be subject to this in one way or another.

The problem is a HUGE reservoir. This reservoir contains a lot of air at the end of the fill. Remember that air is compressible, whereas ink is not.

So with such a huge volume of "elastic" air behind the ink at the very end of a feed, it’s easier for the pen to break the surface tension and lose it’s vacuum once the ink level gets real low.

Remember that really, this only happens at the very last end of the fill. This can be avoided just by filling if you are in doubt.



The air temp theory is certainly not mine (and you don’t have to go far to see it being put forward as fact). I agree it would seem more logical if it were gradual (more air means more that could expand) unless there’s some barrier potential before the pressure become great enough. It does seem that some cheaper pens, when converted, are prone to burp when as much as half full (a Preppy for example). Perhaps the higher quality feeds you use are better at mitigating this factor.

As to filling systems that would be susceptible, many other methods offer some insulation by containing the ink in some chamber that is separated from the barrel by air. Still, bulbs or pistons should suffer it to some degree, unless reduced capacity saves them.

Just pondering. Like I said, not my theory, but I encountered it almost as soon as I got into fountain pens.

I certainly wasn’t trying to shoot down your theory, I’m sure that it has some effect, but not a lot, my opinion.

//Perhaps the higher quality feeds you use are better at mitigating this factor.//

This is definitely a factor. A quality feed will have plenty of combs to soak up excessive ink, and help regulate these issues.

I probably will do some tests someday, just for my own curiosity.



RE comment about burp when ink is low.

That is consistent with pens leaking at altitude on aircraft. Some pens seem to be insensitive to altitude, but those that do sometimes leak will not leak if fully filled with ink.

This is a little late but I hope it will give some food for thought regarding heat and air expansion: The chances of a burp coming from your hand warming up the air inside the pen and causing enough expansion to force the air out seem low to me. Pressure increases proportionately with temperature in a set volume. From 0 C to 100 C pressure increases 33%. To double pressure you have to double the Absolute Temperature, starting at 273 K or 0 C and end at 546 K or 273 C.

At the temperatures we live in you roughly average an increase or decrease of volume by 2% for every +/- 10 degrees F. If you are heating your pen up 30-50 degrees rather quickly then that extra volume from expansion may be enough to overcome the surface tension of some or most inks. Say the pen has a pressure of 1 ATM at 60 F inside: 100 kPa, 14.7 psi. Heat it up to 80 and your pressure increases to 107 kPa or 15.5 psi. The pressure has changed by nearly 7% or .8 psi, I have no idea if that is enough to cause a burp or not and I have no idea what the internal pressures really are to start with but it gives you an idea of the minor change in pressure brought by a large temperature change.

I think the reason a Preppy burps easier is the cheaper feed system and I agree that a burp comes from a sudden loss of the "vacuum" that has formed, be it a combination internal and external temperature changes, amount of surface tension the ink has and quality of pressure equalization in the feed system. As I understand it the feed system was improved specifically to stop burping.

Hello Brian,
I had an experience with an ED conversion (not one of your pens) where the ink literally ran out through the feed as soon as the pen was put together. I think this was an extreme example of the weight of the ink being enough to let gravity do it’s job. I think there is also an element of the surface tension breaking more easily when there is more air above the ink.

Hi Gordon. Very doubtful that this has anything to do with gravity or the weight of the ink. Most likely, there’s a leak somewhere. Does the pen have a blind cap? If so, this needs to be sealed.

I’m finding it’s a lot easier and more precise to use a small syringe (no needle) to fill either a pen or a portable inkwell than to use an eyedropper. Much less messy, much easier to clean out afterwards, and, like I say, much more precise because syringes are clearly labeled with measurement marks. Easy and cheap to buy, too.


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