How to Use a Vacuum Filler Fountain Pen

Vacuum filler pens hold more ink than almost any other filling system. Here's how to fill one correctly, with specific guidance for TWSBI vacuum fillers.

What Is a Vacuum Filler?

A vacuum filler uses a plunger mechanism to create a vacuum inside the barrel, which draws ink in rapidly and in large volume. Unlike a piston filler, the plunger doesn't stay inside the ink chamber, it seals the barrel after filling, maximising ink capacity.

TWSBI is the brand most associated with vacuum fillers in the modern pen market, with models including the TWSBI Vac700R and TWSBI Vac Mini. This guide uses TWSBI terminology, but the principles apply to other vacuum fillers such as the Pilot Custom 823. For piston filler pens, see our separate guide: How to Use a Piston Filler.

What You'll Need

Your vacuum filler fountain pen
A bottle of fountain pen ink
A paper towel or lint-free cloth

Step 1: Unscrew the Blind Cap

On a TWSBI vacuum filler, the blind cap is the flat knob at the end of the barrel. Unscrew it to expose the plunger button underneath. Do not remove it fully, just loosen it until it moves freely.

Step 2: Push the Plunger Down

Press the plunger button all the way down. This pushes the plunger to the bottom of the barrel, expelling any air or residual ink and preparing the chamber for filling.

Step 3: Submerge the Nib

Dip the nib and section into your ink bottle. Submerge as deeply as possible, ideally up to the barrel threads, to minimise air intake during filling.

Step 4: Release the Plunger

Slowly release the plunger button. The vacuum created as the plunger rises draws ink rapidly up into the barrel. You should see the ink level rise visibly through the demonstrator barrel (if your pen has one).

Don't rush this step. Releasing the plunger too quickly can cause ink to splatter inside the cap or draw in air bubbles.

Step 5: Repeat for a Full Fill (Optional)

For maximum ink capacity, push the plunger down slightly with the nib still submerged to expel a small amount of ink and any trapped air, then release again. This tops up the fill and removes air gaps.

Step 6: Wipe and Seal

Remove the pen from the bottle and wipe the nib and section clean. Then screw the blind cap back down firmly to seal the plunger in place. This is important, leaving the blind cap loose can cause the plunger to shift and ink to leak. If your pen develops a leak, see: How to Fix a Leaking Fountain Pen.

Step 7: Cap and Write

Cap the pen and it's ready to use. TWSBI vacuum fillers hold a substantial amount of ink, the Vac700R holds approximately 2.1ml, so you should be writing for a long time before needing a refill.

TWSBI-Specific Tips

Keep the blind cap tight when writing. A loose blind cap is the most common cause of ink flow issues on TWSBI vacuum fillers. If you're experiencing flow problems, see: How to Adjust Ink Flow on a Fountain Pen.
Use TWSBI Seal Grease on the plunger O-ring periodically to maintain a good seal and smooth action. TWSBI includes a small pot with most pens.
Disassembly for cleaning: TWSBI vacuum fillers are fully disassemblable. Use the included TWSBI wrench to unscrew the nib unit, and the barrel can be flushed or fully taken apart for a deep clean.
Ink visibility: The clear barrel makes it easy to monitor ink levels, no need to guess when you're running low.

Cleaning a Vacuum Filler

Fill with lukewarm water using the same plunger method, expel, and repeat until the water runs clear. For a deeper clean, disassemble the pen using the TWSBI tool and rinse each component individually. A bulb syringe can also help flush the feed, see: How to Flush and Deep-Clean a Fountain Pen with a Bulb Syringe.