# Sealing a cap



## msoulier (Jun 25, 2018)

Hi,

One problem I've noticed with the fountain pens that I turn is that the cap does not keep the nib dry for all that long compared to mass-produced fountain pens. I'm thinking of trying silicone to seal the cap and I'm wondering if anyone else has tried this, or has a technique to seal the cap to keep the nib wet.

Thanks,
Mike


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## More4dan (Jun 25, 2018)

msoulier said:


> Hi,
> 
> One problem I've noticed with the fountain pens that I turn is that the cap does not keep the nib dry for all that long compared to mass-produced fountain pens. I'm thinking of trying silicone to seal the cap and I'm wondering if anyone else has tried this, or has a technique to seal the cap to keep the nib wet.
> 
> ...



Are you wanting the nib kept wet or dry?  You seem to be asking for both in the post, or more likely I'm just a bit dense on a Monday.  I use my FP daily and haven't had a problem with the ink flow starting (wet).  I store it nib up.  The cap is aluminum lined with Claro Walnut on the outside with aluminum to aluminum threads.  

I've had a Graduate Magnetic FP that would not only dry the nib but the entire reservoir would evaporate in about a week's time stored nib up.  I've also had several nibs (Bocks) that would not feed ink correctly because the tines were spread too far apart (too wet).  After tuning I was able to get them to perform correctly.  My JOWOs have been better behaved in that respect.  

Danny


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## Curly (Jun 25, 2018)

A thin O-ring might work and not be as potentially messy. The trick is finding ones the right sizes.


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## Pierre--- (Jun 25, 2018)

I had the same issue with wooden caps. A Q-tip and three layers of varnish solved the problem: now, I can forget the nib two weeks in its cap, and then it will write as new.


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## jalbert (Jun 26, 2018)

The nib's propensity to dry out is largely dependent on how well the nib is sealed off from the rest of the cap when the pen is capped. For example, most fountain pens will have a shoulder inside the cap that the end of the section butts up against to create a seal when the pen is capped. This prevent air from getting to the nib and drying the nib out. 

Another possible factor is if the inside of the cap is a porous material such as wood, that allows moisture to be absorbed. 

If you are having problems with a kit pen, I'm not sure how you would work around that. If you are talking kitless, then  designing the pen in a manner that seals off the nib would be your best bet.


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## Pierre--- (Jul 3, 2018)

jalbert said:


> most fountain pens will have a shoulder inside the cap that the end of the section butts up against to create a seal when the pen is capped. This prevent air from getting to the nib and drying the nib out.




That is one thing I don't clearly understand. On one hand, nibs are sealed. On the other hand, there are air holes through the cap. The latter I found useful on eyedroppers. I don't see where the theory is. Any ray of light, John or others?


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## Curly (Jul 3, 2018)

I just took a look at an old Sheaffer leaver fill that I have. It has a hole in the side of the cap behind the cap threads before a shoulder that seats against the forward face of the section. It would seam that the hole will vent the cap until just before the cap is seated. Without the hole the air would have no place to go while being screwed on.


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## monophoto (Jul 3, 2018)

msoulier said:


> Hi,
> 
> I'm thinking of trying silicone to seal the cap and I'm wondering if anyone else has tried this, or has a technique to seal the cap to keep the nib wet.



Short answer:  no.

If you are referring to a kit pen, there are two cap arrangements to consider.  A snap-cap is almost always loose, and there really isn't a way to seal it.  If the kit features a screw cap, the threads are press-fit into the brass tube, and that arrangement should be pretty tight.

If you are referring to kitless designs, then you are probably (but not necessarily) using some kind of plastic (aka 'resin') for the body, and it will be reasonably tight.  And kitless designs usually feature a threaded cap.

I have lots of fountain pens - some commercially made, and some shop-made.  And the experience I have had with them drying out is all over the map.  I have an El Grande (kit) that seems to stay wet forever.  Likewise a plastic Lamy Safari, and also a no-name metal pen.  I also have some kit pens (both CSUSA and PSI kits) with snap caps, and a no-name commercial metal pen that will dry out if I don't use them for four or five days.  And I have a very expensive Mont Blanc that would dry out if I didn't use it a few days - which is one of the many reasons I no longer use it.

The solution is to use your pens frequently.  And if you are using several pens simultaneously, set up a rotation scheme so that you use a different pen every day.


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## jalbert (Jul 8, 2018)

Pierre--- said:


> jalbert said:
> 
> 
> > most fountain pens will have a shoulder inside the cap that the end of the section butts up against to create a seal when the pen is capped. This prevent air from getting to the nib and drying the nib out.
> ...



The breather holes allow the cap to screw on while expelling air so a vacuum doesn't build up into the pen through the nib...which will slowly release expelling ink with it. the holes are drilled before the shoulder, so the nib will remain sealed off when fully capped. You don't see this much on modern or custom pens though. I use big square threads, and don't cut them extremely tight, so vacuum build up isn't really an issue that I've had.


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## Pen Ingeneer (Nov 12, 2018)

Curly said:


> A thin O-ring might work and not be as potentially messy. The trick is finding ones the right sizes.



If you have any O ring of the cross section you like, you can cut it and glue it end to end with some loctite superglues. :glasses-nerdy:


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## Pen Ingeneer (Nov 12, 2018)

Pierre--- said:


> jalbert said:
> 
> 
> > most fountain pens will have a shoulder inside the cap that the end of the section butts up against to create a seal when the pen is capped. This prevent air from getting to the nib and drying the nib out.
> ...



The hole is supposed to be outside the sealed section...:glasses-nerdy:


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## Pen Ingeneer (Nov 12, 2018)

monophoto said:


> msoulier said:
> 
> 
> > Hi,
> ...


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## Curly (Nov 12, 2018)

Pen Ingeneer said:


> Curly said:
> 
> 
> > A thin O-ring might work and not be as potentially messy. The trick is finding ones the right sizes.
> ...



True with neoprene and rubber. I'm not so sure about silicone rubber. The real challenge would be to get the right length and aligning those tiny ends when you put them together. It was easy enough when I did it with big o-rings but now I think that's when the shakes show up and the eyes ain't what they once were. :wink: 

Welcome to the forum.


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## frank123 (Nov 12, 2018)

I don't understand the problem of drying out the nib to where it gives problems starting unless some inks cause the problem and the ones I like using don't.

I just picked up a pen that has been sitting (stored nib up) for over a month without using it and had it start immediately with no problems only holding down for about a second or so before I started writing.  

On the (cheap) commercial pen side, I've let a Pilot Varsity disposable FP sit for well over a year and still had an instant start with it.

I suspect either a nib to feed fit problem or an ink problem if this isn't the case with yours, and I'm a very amateur pen maker, who doesn't make many, so take that as my opinion only and don't put too much faith in it.

FWIW, I just do an occasional kitless FP and generally use ebonite feeds which may have better feed flow characteristics than those plastic things that come with the kits.  Maybe someone could try using an ebonite feed on the same pen that is having dry out problems with a plastic one and giving starting problems to see if it makes a difference or not.  Video's of feeds I've seen seem to show the ink flowing back into the chamber when the pen is turned upright and then back again when held in the writing position (this can be directly observed in a Varsity), maybe some feeds or inks leave just too much residue caught in the feed channels that is drying and stopping them up?


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## Harley2001 (Nov 12, 2018)

If you look on old pens there a innter cap that fits on top on the section to help with that but you don’t want your nib to dry out it should be wet .


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## Pen Ingeneer (Nov 12, 2018)

Curly said:


> Pen Ingeneer said:
> 
> 
> > Curly said:
> ...



Thanks for your welcome 

try making an assembly gig from polyprop, superglue doesn't stick to it.  I would choose a neoprene, it works better with a slide friction when used in a screw on cap.  There is no need for much compression to achieve a good seal especially when combined with a metal sleeve.  Silicone is always a bit sticky.  With silicone, use silicone glue, I would say.


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