Today, Friday the 14th of May, I learnt two important things as a result of apparent nib leakage on my recently repaired Parker ‘New’ Duofold Senior. Now before I cover them I should point out that I did not break the pen nor was it errors on my part (well not quite, as I shall explain), but first I would like to thank Mike McShane of The Pendragons for the advice and corrections he gave me this afternoon while I asked for confirmation on what I was about to do.

To back up slightly, having not used the pen for a fortnight or so about five days back I uncapped it to find ink on the section and in the cap and none in the sack. I cleaned the pen, refilled and tried it. All seemed fine. I did wonder if the spring bar was applying pressure on the top of the sac when closing the barrel, but a careful check showed this to not be so. Today I uncapped the pen to use to find ink once more on the section. Worried I went to flush it with water but the sac would not fill. Removing the metal frame showed that the sac had split on the edge as if the one I had used was too narrow. I had a spare latex size 17 near by for another project and on trying it the larger sac snuggly fitted over the peg. Next stop was to order a size 17 silicone sac (previously it was a 15 and The Pendragons do not have a silicone size 16), but for safety I decided to check with Mike to make sure I was doing the right thing, rather than getting another size 15 or the sac for a 51 Aeromatic as the sizing of the frame on those seem to be the same width as on the 1950s UK/European Duofolds. I’m glad I did and learnt the following:

Looking at the photo below you will notice the opening of the previous sac was pinched in. I assumed this was normal as the length matched that of the original sac.

Now normally on a latex sac you would trim to fit but they are straight so I assumed everything was fine. Lesson 1. That pinch on the silicone sac is actually part of the injection moulding process and so should be cur off. The size is based on the wider part and this would explain why it proved to be so hard to get the sac on in the first place. This was why it was too tight and the reason why it was split by the edge of the peg.

As for lesson 2. I, as is my normal practice, stored my pen on it’s side. Apparently the silicone used for the sac is air permeable¹ (oh and is also not the same as silicon, which is a natural element not a polymer… – so lesson 3) with the result that if you do use a silicone sac in a fountain pen then that pen should be stored cap up else there is a risk of ink being pushed out, just as happened to me. While the pen previously had a clear sac this was not of the same material as the modern ones and also no longer available (or not easily anyhow).

So this actually left me with a couple of choices. The present sac had split in the part which should have been trimmed off and so could be re-used, however this would also mean I would have to remember to store the pen upright, something I’d prefer not to do, partly as I do not have anywhere suitable to store it and also because I would quite probably forget. The other option was to use a latex sac. As well as the spare size 17 I mentioned above I also had a size 16 left over from when I repaired an Esterbrook K2². Down side was I would no longer be able to see the ink level. Thing is, on the more modern aerometric pens (such as the Parker 51) and the bar converters that spawned from them, you can’t see the ink anyway and so that’s the route I decided to take. Also as previously mentioned, I tend to leave my pens on their side by default.

First the sac needed trimming down to size. As the silicone one had been just on the limit of what would fit I cut the latex one to be slightly shorter for safety.

Next was a test fit as the last thing I needed was the embarrassment of a larger sac falling off, then it was shellac time.

Now I just need to wait for it to cure/harden. If you think back to my previous article you may remember my mentioning uncertainty about how long to leave the Duofold before testing and how in the end I gave it 8 hours as some people recommended leaving the pen over night. Recently The Pendragons redid their website as well as some of the guidance on it. The recommendation they give is a full 24 hours, so this I am presently doing and will continue this update tomorrow.

Carrying on the next day….

In my mind I knew all would be fine with testing, but still things could have gone wrong, after all I’m not exactly experienced at this. Still the water test showed it drawing in liquid without leaking, then when held above the bowl, squeezing the sac showed a reasonable amount of liquid being ejected. Again no leaks.

And so once more it was time to dust with French talc. Now while I was uncertain about whether this step was really needed for a silicone sac, latex can catch/drag on the frame and the inside of the barrel so dusting was required.

Brushing off the excess I carefully slid the metal frame back in place then inserted the pressure bar.

All that was left was to ink the pen…

…and then test it. Of course the real proof of success will be in about a week time with the pen still working and no ink seepage on to the section.

Six days later…

And now a week on from the start of the post and I’m happy to report all is fine and dandy. The pen had been left unused on it’s side, so today was the first time the cap was removed and the Parker tested. No ink on the section or in the cap and the ink flowed first time.

Hopefully my beginner mistakes on how to use a silicone sac as a replacement and the downsides to one in a pen (cap up storage) may help some of you and also show that if something does not go right for some reason, as long as you’ve been careful it is not the end of the world and you can have another go.

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1. On the air permeability of silicone sacs. David Nishimura of Vintage Pens in the USA has a FAQ on his site which includes the following information in the 3rd paragraph from the bottom of his page:
   “Silicone’s main disadvantage is its permeability to air and water vapor. Ink will dry out more rapidly in an unused pen with a silicone sac, and it is advisable to leave a silicone-sacked pen with its nib elevated when not in use to prevent gradual ink seepage into its feed. Silicone is not as tough as latex, so should not be used for high-stress applications such as twist-fillers and Vacumatic diaphragms. Pressure bars with sharp edges are more likely to tear a silicone sac than one made of latex.“
2. There are lots of resources on line for repairing and Esterbrook however I found contradictory information on whether the K2 needed a size 14 or size 16 sac and this was before I a set of measuring callipers, so being cheap and for safety I went for both. The size 14 was the correct one and so I was left with the 16 as a spare, which proved fortunate this week.