Air Block In A Sac

[Beechwood]

My daily pen is an Airmail eyedropper that uses a Burnham nib and section that still has a sac in place.

 

When the pen needs filling I simply squeeze the sac and refill. To have more ink capacity I changed the black rubber sac to a clear sac, almost the full length of the Airmail. The problem is that the ink doesnt want to flow down the sac to the nib, as if there was an airlock, I then cut down the sac to see if a reduced length of sac might assist, it didnt.

 

So I squeezed the air out of the sac, but, of couse, as soon as I released the sac new air came in from the nib.

 

It is as if the sac has more cohesion with the ink.

 

The ink in use is the new CdA blue.

 

Any ideas?

Edited April 16, 2014 by Beechwood

[Moshe ben David]

Don't know what your clear sac is made of, but it could be a surface tension issue. If you have any Waterman blue inks maybe you could try one of those just to see how it behaves? Waterman inks seem to be pretty wet and free flowing....

[Beechwood]

Thanks MbD, thanks for the advice.

 

The problem was solved by a wash through with a very dilute detergent

[mhosea]

I've had trouble with the pure/true silicone sacs doing this. Sometimes the ink can be shaken/flicked down towards the section.

 

If the problem was release compound still in the sac and you managed to wash it out, then that's great. OTOH, detergent might also solve the issue only temporarily by leaving behind a little bit of surfactant, making the ink flow better. Keep an eye out, and good luck.

[Cepasaccus]

In the cartridges the little plastic ball helps to get the ink to the feed, in the MB converter is a little spring. Maybe you can put something inside the sac (which does not react with the ink)?

 

Cepasaccus

[Beechwood]

In the cartridges the little plastic ball helps to get the ink to the feed, in the MB converter is a little spring. Maybe you can put something inside the sac (which does not react with the ink)?

 

Cepasaccus

 

 

Interesting idea.

 

I havent come across this as a problem so far and perhaps it is only noticeable because the sac is inside a eyedropper pen, therefore it is easy to see.

 

The pen sac was bought bought from a well known supplier. I think that for the future I will wash any silicone sacs before fitting.

[Vintagepens]

This seems to be a not uncommon issue with a number of setups, mostly having to do with the relatively low wettability of many plastics when combined with a narrow ink reservoir (though a friend has been having the same issue with a glass-cartridge Waterman, even though glass is quite wettable).

 

The idea is sound, to use something to break up surface tension and to dislodge the ink. Another possibility with a sac is to put in a length of a highly wettable material, such as horsehair or some other organic fiber. A very thin rod or flat strip of hard rubber would also work well.

[Ernst Bitterman]

A very thin rod or flat strip of hard rubber would also work well.

 

...as Parker used in the 17; a proven technique.

[mhosea]

I don't know how "wettable" Teflon is, but I just had some pretty decent results from inserting a length of the Teflon tubing that David sells into a spent Sheaffer cartridge with the end cut off and testing with plain water. I tried it both divided longitudinally and whole. It seems to work best when the Teflon can move lengthwise a little, so just inverting the pen from pocket to writing position might release the ink as the Teflon length falls forward.

[Beechwood]

The problem was fixed by a wash through of very mild detergent but I think that there are a number of better, mechanical solutions that have been suggested above.

[mhosea]

The problem was fixed by a wash through of very mild detergent but I think that there are a number of better, mechanical solutions that have been suggested above.

 

FYI, I thought I had solved the problem that way as well, but in my cases I was proven wrong over time. The problem recurred.

[Beechwood]

 

FYI, I thought I had solved the problem that way as well, but in my cases I was proven wrong over time. The problem recurred.

 

I will see if I can find a small glass bead or pearl and report back

[mhosea]

 

I will see if I can find a small glass bead or pearl and report back

 

 

https://www.fountainpennetwork.com/forum/index.php/topic/258016-ink-surface-tension-in-silicone-sacs/

[Beechwood]

 

 

https://www.fountainpennetwork.com/forum/index.php/topic/258016-ink-surface-tension-in-silicone-sacs/

 

 

Thanks for the link.

 

I had also bought the sacs from the same seller. Last night I put a new silicone sac on the pen and inserted a small ball from a Cross cartridge. The results are not perfect, but improved. Surface tension or 'ink sticking to the far end of the sac' still seems to be there but the ball runs up and down the sac taking a little ink with it each time, which, on first tests at leasts, appears to be enough to keep the feed inked.

 

Never had this problem before, or at least I wasnt aware that there was a problem and might have just put the nib drying up down to poor flow at the feed, no thinking that the problem could be upstream.

 

I have also never seen this problem on other clear sacs or cartridges.

 

Other pen users who have fitted silicone sacs may not even be aware of the issue, the problem may exist but because you would not usually be able to easily see ink being blocked in the silicone sac if they have been fitted to pens that are not that easy to open up. The fact that I have only seen this problem is only because I am using the sac inside an eyedropper body.

 

It is possible the problem with silicone sacs is more common than thought.

 

I will persevere with this modification and see how the Cross ball in the sac works out.

 

 

 

I

Edited April 24, 2014 by Beechwood

[mhosea]

I do think it is more common than is realized, but it is also not as relevant as it might be because the primary use case for silicone sacs is in collector-grade vintage pens that would otherwise be at risk for discoloration or worse from latex and PVC sacs. The longevity and chemical resistance of silicone is an argument in favor of them for users, but the gas permeability is an argument against, as is this flow issue, IMHO. So for users it's a debate, but for collectors it tends not to be much of a contest. You can use the pen a bit if you want, and it's consistent with preserving the pen. I've switched back to latex for my users, but I also use silicone sacs in some of my collection pens. It's unfortunate that nothing we have is perfect, but c'est la vie.

Edited April 24, 2014 by mhosea

[Ernst Bitterman]

I'm a user, but I also incline towards the silicone sacs where there's likelihood of discolouration. This isn't a problem I've really noted, but most of the pens I've got silicone in have a #16 or larger (surface tension being a greater issue in a narrower space). I'm just curious as to the size of sac Beechwood is having the problem with.

[Beechwood]

I'm a user, but I also incline towards the silicone sacs where there's likelihood of discolouration. This isn't a problem I've really noted, but most of the pens I've got silicone in have a #16 or larger (surface tension being a greater issue in a narrower space). I'm just curious as to the size of sac Beechwood is having the problem with.

 

 

A size 18 Ernest. I must say that the Cross ball whizzing up and down the sac appears to be doing the trick and I cannot think it could be doing any harm.

[Ernst Bitterman]

Interesting (said Artie Johnson style). You'd probably have to give the pen a mighty shake indeed to start denting up the back of the feed with the ball.

[Beechwood]

 

 

A size 18 Ernest. I must say that the Cross ball whizzing up and down the sac appears to be doing the trick and I cannot think it could be doing any harm.

 

 

Whizzing may be over egging the pudding, ink drag doing all it can to slow the process

[mhosea]

I may have found an easy solution to the problem using something I had available. I didn't have a strip of hard rubber or a horse hair, and I didn't want to use anything hard, really. So I sacrificed another silicone sac to make a small strip of silicone that I inserted in the silicone sac when I installed my last one. So far it seems that when I invert the pen, the ink flows a little slowly but without delay from one end of the sac to the other. Will have to see how it goes with a variety of inks.

Edited May 9, 2014 by mhosea