I have see some of the silicone sacs listed for sale. Are they the same sizes as the rubber ones? I assume they last longer than rubber and the cost is not that different so should I put silicone sacs in all pens that I am working on? Would they interact with Hard Rubber? Quick input appreciated as I am ordering today.

Sacs will be ordered for:

Sheaffer Snorkel
Esterbrook SJ
Majestic
J. Harris BCHR

Thanks
Charlie

Charlie, for the Snorkel you are better off with a 14 1/2 thin wall sac instead of the silicone..
The vacuum of the touchdown filler system works better with the thin walled sacs...
You can find them at Tryphon... Giovanni has them and the silicones also...

Yeah, I am calling in an order to him later today. Thanks for the thin wall tip.

i'm not sure they're really that much more durable (though I suspect so to some extent) but the real advantage to a silicone sac is to see ink level. But, as Griz points out - they're not optimal for TDs or Snorks. Just not pliable enough.

Silicone is far more durable and resistant to ink. This is why you find Parker aeros often with good sacs whereas old pens and vac fills with rubber sacs have perished.

Flexibility is a consideration. eg In a lever filler you will find the lever stiffer and the pressure bar comes up against more resistance.

If you can use silicone in celluliod pens definitely do, also for BHR.

Gary

Silicon sacs have little to do with seeing the ink inside. Silicon sacs are used when you are worried about off gasing deteriorating the color on vintage plastic pens. Otherwise, conventional sacs are perfectly fine.

Roger W.

i didn't say that was why they were used - i said it was an advantage.

I don't have much in the way of lever fillers and have used latex for those I have. But the silicone have worked well for pens that were cartridge only and for which carts are nigh impossible to find. much easier for me to see how much ink is in those particular pens than to guess.

I bow to the expertise of all the well... experts, as to their other properties.

Roger-

By your reasoning then, a silicone diaphragm would be ideal for a Parker Vacumatic so that the clear celluloid would be kept from ambering?

I wonder if they make silicone diaphragms... I didn't see one on Tryphon.

This is a non sequitur. The sacs in Parker aerometric pens are not silicone. They are Pli-Glass, which is a nylon that was formulated specifically for use as pen sacs.

Silicone is not more durable than latex. It is less stretchable and less flexible. It probably lasts longer if you don't use it, but I do not think the jury is in where its ultimate longevity as a pen sac is concerned. Silicone's lesser flexibility makes it inappropriate for Vacumatic diaphragms because a diaphragm of silicone that is sturdy enough to stand up to use would also be too stiff to evert properly. For use as an ordinary sac, you can't always install a silicone sac of the proper size to prevent heat transfer from the user's body -- this is because the sac nipple on the section may be too large to allow the correct sac to fit over it without splitting. (Note, please, that the correct sac is not necessarily the one the manufacturer used. Manufacturers had three criteria for sac size: ink capacity, ink capacity, and ink capacity. This means that they frequently used sacs that were technically too large.)

In terms of use for pen sacs, silicone has one, count 'em ONE, advantage over latex. It does not outgas sulfur compounds, and it will therefore not contribute to further discoloration of celluloid. For any aplication except in celluloid pens of discoloration-prone colors, silicone sacs are inferior to latex.

Richard, and Roger and anyone else who has the knowledge to chime in:

My understanding is that the discoloration prone celluloids are the early Jade, Lapis, Black-and-Pearl, Sheaffer Black-and-Blue, and Parker True-Blue. I may be missing one or two.

Is the Ambering of later transparent celluloids, like the various Parker Vacumatic and Sheaffer Balance stripes, Ebonized pearl, etc part of the same process? Or a different beast altogether? Is it better to resack an Ebonized Pearl balance with silicon, or will that not help prevent ambering and age-darkening?

John

Richard, yeah I knew aeros were some form other than rubber. So to avoid confusion is the latex you refer to the black rubber sacs we commonly get for repairs.
Thanks for putting us right btw.

Gary

edit:- Just answered my own question, thanks.Doh.. :doh: What did I have for breakfast ?.

You've missed a couple.

Everybody's Jade
Everybody's Lapis
Black-and-Pearl (Waterman called this color Nacre)
Sheaffer Black-and-Blue
Parker True-Blue (Parker called this color Modernistic Blue)
Onyx (Waterman)
Moderne Green (Parker)
Marine Green (Sheaffer, both the Pearl and the striated versions)
Ebonized Pearl (Sheaffer)


Yes, it is. The process is oxidation. Sulfur, like oxygen, has two electrons in its outer shell and usually carries a -2 valence. It is a less active oxidant than oxygen, but the reaction is basically the same.

awwww...come on... you don't think it's nice to be able to see the ink level?

seriously though - are the sacs in the cheapie pens like Heros also Pli-Glass?

No, they're not pli-glass. They use silicon sac's in aeros like that for visibility purposes alone. They certainly aren't protecting celluloid...

The flexibility loss over latex isn't a concern like it would be in lever fillers (where visibility doesn't make much sense anyway <_<).

Gerry

Although I'd read and accepted that Parker's Pli-Glass sacs were nylon, I recently was in conversation with others who suggest that PVC is more likely the correct ID.
For various reasons, this makes good sense -- though we are still awaiting definitive testing.

Should we not also look at the fact that silicone is not going to be attacked by the ink in the same way as latex. And will certainly not rot out in the same way so life time should be a factor longer. I still offer to replace sac's I put in for five years after a change if they fail for free, so most customers wont need to worry.

We use Silicone sac's in lever fill pens and to be honest have not noticed a huge change in lever tension over latex sac's. There is a slight increase but in a pen with a sturdy lever set up this is not an issue. I dont think we would use silicone in a Conway Stewart.

I would how ever echo one note sac size is very important but with out too much effort the silicone sac fill fit on the nipple and stay put much better than the latex.
When the silicone sac is cut to length the most important thing is to get a clean cut
VERY CLEAN we use a 10a scalpel blade and try to end up with no tool marks on the cut end. The silicone will try to split if the end is ragged.

kevin


www.pen-time.biz

Hi,

I use Silicone sacs because I have found that they last much longer than the latex ones. I have given my silicone sacced pens testing by filling and emptying the pen hundreds of times. Nothing happened. Latex sacs always fail my testing because they would not stay put and sometimes, they would tear up inside. That of course would not happen to the latex sacs in real life because they are not subjected so vigorously.

Dillon

Do you mean that you would not use silicone sacs in vintage Conway Stewart lever fillers ?

try this experiment. take a silicone sac and bite into it. teeth marks will work all the way to the inside of the sac. try the same with a latex sac. it will be unaffected. what your teeth does to the sac, a pressure bar will also.

other experiments you can try involve pulling on the sac, cutting it with a blunt blade, etc. in all cases, silicone sac as sold by woodbin easily stretches, tears, etc.

as far as durability goes, silicone cannot hold a candle to latex.

now regarding the pli-glass sacs---they are the most durable, but the ones in hero pens are sometimes nylon. in fact, i have cannibalized hero pens for precisely this purpose! the ones that have a rubbery feel instead of a polythene feel are probably silicone but mixed in with some kind of plastic. they are much stronger than woodbin silicone sacs.

If someone is willing to sacrifice (test is destructive) a sac and send it to me, I could run an FTIR analysis on it and identify it as nylon vs pvc.