Mentmore Ink-Lock Vacuum Filler

The ink-in-the-barrel pen has always seemed like a good solution, mostly because it has the potential to have great capacity. The original ink-in-the-barrel pen was the eyedropper, but manufacturers wanted to add a self-filling ability. The grand-daddy of them all is De La Rue’s Onoto plunger-filler, which dates back to 1905 and remains, in my opinion, the all-round best of the ink-in-the-barrel pens. It wasn’t until 1925 that another came along, Chilton’s Pneumatic Filler. Parker’s Vacumatic* followed in 1933 and Sheaffer produced the Vac-Fill, virtually a revamp of the Onoto system, in 1935. Last – and least known – is the Mentmore Ink-Lock in 1938.


The name Ink-Lock doesn’t refer to the filling system but to a patented method of shutting off the ink when the pen was capped. There are also lever filler and button filler Ink-Locks. This ink-in-the-barrel filling system was given its first outing in the Platignum Visi-Ink. Pressure in the barrel is reduced by forcing air out through the feed channels by squeezing a bulb, thereby drawing ink in. This is repeated several times until the pen is full. In principle, this method is less like the superficially similar Parker Vacumatic and more like the Chilton.

“My!” you’re thinking, “How clever Deb is to have sussed all this out by her little self!” The truth, sadly, is that when presented with this strange pen that didn’t want to come apart I cried a little and stamped my foot. Then I sent it to the estimable Derrick Purser:

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who puzzled out the workings of the pen, manufactured some parts that were missing and also provided me with information on the filling method. Much kudos to Derrick!


Mentmore Ink-Locks are far from common, and I would even go so far as to say that this version is somewhat rare. Why? Not because it was a bad pen, far from it. I suspect it was a misfortune of history. The pen was produced not long before World War II, and I suspect that it was dropped in favour of the simpler designs like the Autoflow as war shortages began to restrict the industry. However, we still have this pen to remind us that Mentmore was once the most innovative of British pen companies.


Mentmores of this period usually have a family resemblance to one another, but the Ink-Lock breaks the tradition. It has a most un-Mentmore-like washer clip of a vaguely arrow-shaped design held by a stud. The feed, too is quite unlike the usual Mentmore feed. The combination of a narrow and a medium cap ring is unique among the company’s output, as, I believe, is the very attractive brown/pink/red marbled celluloid.

*I suppose that the withdrawal of air as a motivating principle is especially obvious in all these pens, hence the names like Vacumatic, Vac-Fill and Pneumatic Filler. However, it is worth mentioning that these pens are no more dependent on the vacuum principle than the less complicated lever filler or the more efficient piston filler. All self-filling pens use vacuum. Prove me wrong.

6 thoughts on “Mentmore Ink-Lock Vacuum Filler

  1. Thanks for the illuminating piece on the Ink Lock, I have just one of these , marked Mentmore Ink-Lock Pat applied for, a button filler with a couple of holes in the cap, set at an angle, as if the cap had been meant for an earlier clip arrangement.

    Excellent quality and as good or better than anything else of the period.



    1. Hi Graham,
      You’re right about the quality. These pens have to be handled for one to appreciate just how well constructed they are. My one has three holes in the cap – two high up and one lower down. The upper ones are actually blanked by the blind cap and so serve no purpose now. They might have had a purpose in assembly, when the blind cap/ink lock sub-assembly was installed. Or maybe not! I’m just speculating here.

      Glad to have informed you a little more on your pen. That’s the main purpose of the blog!

  2. big thanks from me too Deb, especially for telling us that additionally there were button and lever fill Ink-Locks. I’ve just bought an Ink-Lock from an ebay seller, and the pen arrived today with, much to my surprise, a standard button system. Seeing that mine is not the more complex filling system shown in Oldfield’s book and your pen, I was almost on the point of slagging off the seller for a wrong description, but…………. thanks to your notes I now realize that there were variations on the type of filling system for these Ink-Locks.
    Mine has the correct clip, Ink-Lock nib, barrel imprint and thin plastic rod in the cap that pierces the feed and shuts off the ink, so would seem all o.k. MIne has two pairs of opposed diagonal placed holes in the top third of the cap, with two opposed singles breather holes further down.

    My pen is black, and has two equal sized gold coloured cap rings. Not important for you to reply, but any idea if the button filler examples were earlier or later than the filling system on your pen which you have dated to 1938?

    many thanks Paul.

  3. Were Mentmore “related” in anyway to Conway Stewart? Checking Mentmore FP’s today I find that a grey-marble Mentmore “Ink-lock” has a Conway Stewart Cap-clip and Gold Nib ?? (the pen looks perfect…)

    1. No, they’re not related. This would be a later repair. Several manufacturers used the same thread and the repairer was lucky to find a cap that fitted. You have a unique pen!

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