A Guide to Fountain Pens with Sealing Valves

One of the key fountain pen characteristics responsible for gaining fountain pen loyalists is ink flow. A well functioning fountain pen will require virtually no pressure from your hand. As the pen makes contact with the paper, the ink smoothly marks the page with each stroke. And with this ease of movement, you can write pages without experiencing strain or interruption. The only hurdle left to continuous writing is how much ink your pen can hold before needing a refill. To overcome this limitation, many users turn to pens that utilize the whole pen barrel for ink. While this solution may seem obvious, more ink equals longer writing sessions, right? It creates a new problem of too much ink flow. In comes another innovative mechanism to add to the list of fountain pen options, the sealing valve.

Fountain Pens with Sealing Valves

There are two main fountain pen types that utilize sealing valves we carry at the shop, vacuum fill fountain pens and eyedropper fill fountain pens. Since the larger ink capacity and flow can be subject to changes in air pressure, fountain pen makers designed this handy mechanism to prevent spontaneous bursts of ink referred to as burping. The sealing valve creates an airtight chamber for the ink, which works together with o-rings and sometimes silicone grease placed where the pen pieces holding ink fit together. The sealing valve is a rod within the barrel of the pen which attaches to a blind cap at the end of the pen. When the blind cap is unscrewed to extend the rod out of the pen barrel, ink flows into the opening inside of the grip, continues into the feed, and then flows through the nib onto your paper. As the blind cap is tightened, the other end of the rod plugs the opening to the feed and no ink flows out of the barrel. The pen will continue to write with whatever ink remains in the feed. After it’s used up, the pen will stop writing until more ink is released by opening the blind cap again.

Pilot Custom 823 and TWSBI Vac700R

The two vacuum fill fountain pens we regularly carry at the shop are the Pilot Custom 823 and the TWSBI Vac700R. These pens have a metal rod with a rubber plunger at the end to manage the ink flow. Both pens hold an impressive amount of ink. The TWSBI Vac700R can hold around 1.7ml of ink and the Pilot Custom 823 holds almost up to 2.5ml of ink. The TWSBI uses a steel nib while the Pilot Custom 823 is equipped with a large 14k gold nib. To fill these pens, you unscrew the blind cap at the end and fully extend the rod. You then insert the nib in a bottle of ink low enough to cover the vent hole on the nib. While the nib is submerged, ink rises into the barrel from the ink bottle once the rod is pushed back into the barrel of the pen creating a vacuum. You can immediately begin writing since ink has traveled through the nib to the feed and established a flow from the barrel to the nib. When storing these pens, you simply turn the blind cap clockwise on the end until it’s closed to prevent ink from flowing into the section of the pen.

Opus 88 Eyedropper Fountain Pens

The eyedropper pens we carry at the shop utilizing sealing valves are from Opus 88 who specialize in Japanese eyedropper pens, the common name for an eyedropper pen with a sealing valve. These pens have an ebonite rod and a small o-ring at the end to seal the ink from flowing to the feed. To fill these pens, you unscrew the grip of the fountain pen from the barrel and use an eyedropper to load ink directly into the barrel and then screw the grip back onto the barrel. With this filling method, these pens tend to take a little longer to set up. Since the ink is only loaded into the barrel of the pen, the valve needs to remain open for some time so ink can travel from the barrel to saturate the feed. Sometimes leaving the grip loose by one turn also helps get the pen started.

The Perks of the Sealing Valve Mechanism

These pens offer a few other advantages in addition to more ink capacity. The safety valve in these pens reduces the risk of air pressure or movement forcing ink out of the pen. You can bring these pens on a plane and avoid ink exploding onto your belongings. A bonus feature for ink collectors is you can enjoy the demonstrator styles even more as the whole barrel can be filled with ink. Shimmer inks create a magical feel to the pen and the sealing valve also helps to prevent shimmer from filling up the feed when the pen is not in use. The ink capacity is a great match for larger nib sizes like a broad, stub, or specialty nibs that go through ink very quickly.

Cleaning and Maintenance

It’s important to remember how this mechanism differs from the more common cartridge loading fountain pens. If these pens are unused for an extended period of time, getting the ink to flow into the feed may need additional time. It can be like starting up a brand new cartridge pen. Just like when a cartridge is inserted in a new pen, the pen may require gentle agitation or may need to be stored with the cap on with the nib downwards so the ink flow can start up again. Resist the temptation to apply pressure to the nib which could cause damage and as a result prevent consistent ink flow from the nib. 

When it comes to cleaning, you can repeatedly fill and flush the vacuum fill pens until the water comes out clear. The TWSBI Vac700R includes a tool to disassemble the sealing valve from the barrel of the pen, however this is generally an infrequent level of maintenance. Opus 88 pens can be cleaned by unscrewing the grip from the barrel, dumping out remaining ink, and washing out the barrel with water. The nib and grip can be soaked in water or held under running water to flush out ink. For a more thorough cleaning, the nib unit can be unscrewed from the grip and cleaned separately. It's recommended to to let the pen air dry for 12-24 hours after washing it out. If you don't mind your ink being diluted for a little while, then you can go ahead and refill the pen right after cleaning.

Though the rod of these pens can be extended quite far to create more ink flow, it’s best practice to not keep extended for too long so the rod is not snapped or bent from falling.