Sac Pens - How Do They Compare To Pistons?

[Precise]

All of my fillable (not cartridge) pens use a piston, either built-in to the body of the pen, or in a converter. These pens all require a vent, which is a narrow slot cut at the bottom of the ink-supply slot in the feed. It seems critical, but works well.

 

I've wondered how the ink sac pens compare. These pens do not require a vent slot in the feed, though I suspect that many of them use the same feed as piston pens and thus have a vent slot even though it's not needed.

 

So my question is, "How do your ink sac pens compare to your piston pens?"

 

Uniformity of line?

 

Starting?

 

Safety against leaks?

 

I look forward to hearing from you.

 

Thank you,

 

Alan

Edited March 6, 2017 by Precise

[Uncial]

Haven't noticed any starting issues with piston filled or sac filled pens and uniformity of line doesn't seem to differ much. I'm not sure why, but most of my sac filled pens tend to have a very slightly heavier flow just before they run out of ink and only one of my piston fillers does this. It's quite a strange phenomena, but it's happened often enough that I know it isn't my imagination. Never had a leak from a piston filled pen, but many of my sac filled pens will unburden themselves of ink if not left nib up when full. Some have a tendency to randomly burp, but thankfully not regularly.

 

I've tended to shy away from sac fillers lately, mainly because I am not at all convinced of the quality of rubber sacs these days. I have a Conway Stewart that has had the same sac in it for decades and I've used all manner of inks in it. I've a Parker 51 Vac filler that has in the last three years had a grand total of seven rubber vac unit replacements; some of them having even turned to mush in the drawer without ever contacting ink. Word I hear is that silicone sacs are the way of the future, but of the two sac filled pens I own that have them, I have to keep them stored nib up. Not at all sure there is a correlation there, but it does seem strange.

[Bo Bo Olson]

There is no problem with recently sacked lever pens. The old good White (I think the US company was) rubber was good for 30-40 or more years. (Don't know if White which came back close to a decade ago is still around.) I had an Esterbrook that lasted about 60 years.

Chinese rubber is not up to that standard.

Silicon sacs have their own problems...and I'd never re-sac with them. Don't remember the exact problems but it can be looked up.

 

Coin operated Conklin was used by Mark Twain. 1912 Sheaffer invents the lever...Waterman improves on the bedding. Worked fine since.

I never had the problems Uncial had with burping. Nor problems if not kept stored up....but storing up was often said to be the best way to store a pen.

Right now I only have two Esties, a Wearever, and a Snorkel.

 

I live in Germany had surfed the German Ebay back when pens were cheap, so have some 50-60 of them; mostly vintage. If the plastic gasket is shot or getting there or the cork, it will leak.

 

If your cork is shot when you buy the pen....from sitting dry for a couple of generations...you can zombie your pen by soaking the cork by filling the pen with water.....for a week....two days don't do the trick.

You will still need to re-cork....so start saving money.

 

In they are not Ahabs or Twsbi's do not use O rings....in they are not made to be pulled apart every year to re-grease the O ring.

Saving money by using an O ring will kill your piston pen....because you have to yank it apart to grease.

Edited March 6, 2017 by Bo Bo Olson

[the_gasman]

I'm not sure why, but most of my sac filled pens tend to have a very slightly heavier flow just before they run out of ink.

 

I'm pleased to read this as I had noticed the same phenomenum and had assumed that it was something that I was doing wrong in either the re-saccing or the usage.

 

Cheers,

David.

[Precise]

some of them having even turned to mush in the drawer without ever contacting ink

I suspect those were polyurethane. I've had polyurethane shoe soles disintegrate in a few years without every wearing them. I've also had polyurethane foam turn to powder in a few years storage.

 

Some sellers of silicone sacs claim that PVC sacs are often falsely sold as silicone. But PVC isn't necessarily inferior to silicone.

 

Your posts inspired some searching on sac materials. Many posts have links to this:

 

https://www.vintagepens.com/FAQrepair/pen_sacs.shtml

 

It's interesting how my post led to issues that I hadn't even thought to ask about --> sac durability and failure. Clearly this is a very important issue.

 

Rather I was just curious to learn how sac pens (which don't need a vent) functioned compared to piston pens.

 

Alan

Edited March 6, 2017 by Precise

[chromantic]

I only have 1 sac filler currently inked, a NOS Sheaffer Cadet TD with the original sac, along with 8 pistons inked, a Steadtler and 7 Pelikans (purchased in that order). I haven't noticed any difference between the Cadet and the pistons in terms of overall performance. No leaks. The Steadler nib will dry out if unused for too long but it's a snap-on cap (and it's inked with Sailor). If by "uniformity of line" you mean consistent flow, they all pass that test.

[dadbar]

The sacs in my Parker 51 Aerometric pens have to be close to 60 years old at this point and they still work well.

 

I tend to shun from piston fillers due to the complexity of the parts. There is not much to a sac and it is a pretty easy job for the do-it-yourselfer.

 

For the same reasons, I like C/C pens due to the simplicty of it. When the converter breaks, they are cheap to replace.

[Ron Z]

I don't think that the filling system has an impact on the performance of the pen i.e. the way it writes, lays down ink on paper, flow etc. That's primarily a function of feed and nib design. Ink capacity is usually designed to be about the same regardless what filling system was used. (example - the Pelikan 200 through 800 use the same internal mechanism parts and have the same barrel ID) To me the filler is incidental. The difference comes in reliability and cost. A piston filler needs occasional maintenance, but not much. The same with converters. Latex sacs may need to be replaced on occasion. I contend, based on experience, that the ink used can have a big impact, but there are environmental factors too. My observations on sac materials and life are contained in this article.

 

If you want a very reliable filling system that holds a ton of ink, buy a properly restored oversize plunger fill Oversize Sheaffer Balance. If the pen mechanic used the right materials and did the job right, the most the pen will need will be an occasional application of a little silicone grease on the plunger rod. The person doing the work and the materials used do make a difference.

[Jamesbeat]

 

Some sellers of silicone sacs claim that PVC sacs are often falsely sold as silicone. But PVC isn't necessarily inferior to silicone.

 

 

In fact it can be vastly superior. If done correctly, a pvc sac can last a VERY long time. Just look at all the aerometric P51 sacs that are still chooching.

 

I have a feeling that 'silicone' may have become misleadingly generic in the same way that 'acrylic' is used for pen blanks.

 

For some reason, pretty much all plastic pen blanks are sold as 'acrylic', whether they are indeed made of acrylic or if they are made of some other polymer such as polyester or polyurethane.

I don't think that this is deliberate deception, I think it is just stupidity on the seller's part.

[ac12]

I use them both and see no practical difference between a piston and ink sac, for your 3 questions.

 

The only practical difference is practical lifetime.

 

- I figure a latex sac at about 10+ years lifetime.

 

- The pliglass (PVC) sac in the P51 on the other hand have worked fine for over 50 years, and still going strong. So effectively no different than the practical lifetime of a piston filler...your entire life. And it has the advantage of no piston mechanism to dry out and have to lubricate.

[Bo Bo Olson]

Two very, very good links....and somewhat new.

 

"""""to the increased popularity of specialty inks (more on inks for vintage pens here), premature failure of latex sacs has become more common, with new sacs sometimes turning soft and gooey in a matter of months or even weeks.""""

((Dating from the lever shape my '48-52 Esterbrook, which was in Germany where repair of sac pens was 'forgotten' lasted some 60 years before it got too mushy to draw ink. The full dieing of the sac took a year. It was said by many that a sac pen often lasted 30-40 years before one had to re-sac.)))

So it is more the ink than the sac?

Is the restructured White company still making sacs or are they now Chinese?

 

Certain pen repair people do not or did warrentee repairs if the pen is then used with Noodlers or Private Reserve, in once they ate the feed. Noodlers may have fixed that...may not have.

 

To me in Germany Noodlers is expensive imported inks and I have enough trouble trying to get together the basic mainland 100 Euro inks. I have mostly shading inks....and the more saturated inks I own .... I don't know if they are supersaturated or just saturated.

 

Any one know if some of the DA inks like the Royal Blue, are saturated or supersaturated.

[Jamesbeat]

I'd say it's probably less susceptible to mechanical failure than a piston filler too.

 

Not that piston fillers are particularly prone to breakage, but those aerometric fillers are legendary for their reliability.

It's almost a given that an aerometric P51 picked up at an antique store, yard sale or eBay will be functional.

[sirgilbert357]

In they are not Ahabs or Twsbi's do not use O rings....in they are not made to be pulled apart every year to re-grease the O ring.

Saving money by using an O ring will kill your piston pen....because you have to yank it apart to grease.

 

 

I'm confused by this last part...my TWSBI was very simple to grease. Very similar to a Pelikan, I unscrewed the nib unit from the pen and used a toothpick with a small dab of silicone grease on the tip. Spread it around on the inner wall of the barrel and work the piston a few times. Done. I was using the Diamond Mini...maybe they aren't all that easy?

 

I can echo ac12 on the Pliglass sac though. I've had a vintage pen with one and while you could tell it was pretty old, it worked fine. If a pen I owned needed the sac replaced and I was able to choose between Pliglass/PVC and literally anything else, I would go with Pliglass every time.

[ac12]

 

 

 

I can echo ac12 on the Pliglass sac though. I've had a vintage pen with one and while you could tell it was pretty old, it worked fine. If a pen I owned needed the sac replaced and I was able to choose between Pliglass/PVC and literally anything else, I would go with Pliglass every time.

 

Caution there are incompatibility issues with Pliglass/PVC.

You can find the info on David Nishimura's site.

http://www.vintagepens.com/FAQrepair/pen_sacs.shtml

 

There is no one perfect ink sac.

 

[Precise]

I started this thread because I thought maybe I'm missing out on better performance with a sac pen. I considered a modern Conklin with a sac. I have three piston Conklins now and they are quite good.

 

But my conclusion from all of your contributions is that sac pens don't function better than piston pens, and (of course) if the sac fails they are worse.

 

Best,

 

Alan

Edited March 6, 2017 by Precise

[Kelly G]

If you find a great writing pen that happens to have a sac, don't be afraid of it. Changing out the sac is usually simple and doesn't have to be done often, say, every 8 to 10 years, give or take a few years. I have many wonderful pens with some form of sac filler.

[ac12]

An ink sac is just a different filling mechanism.

Cheaper and easier for the manufacturer to make than a piston.

Edited March 6, 2017 by ac12

[Bo Bo Olson]

Sirgilbert...even the brass screw in piston of the 800/1000 is not made to be taken apart often.*** And the more common 200/400/600s not at all. They can be taken apart....but how often before they are shot?

 

Ahabs and Twsbis are made to be taken apart.

 

***Some folks are OCD about cleaning what don't need to be cleaned. Even if one has a demonstrator...it demonstrates that most of the ink stays in front of the piston....and a drop or two after it...is over kill to take that pen apart every time that happens. As long as it don't leak out the back you are good to go. IMO.

 

Rick Papas said a Pelikan should be greased every three years. And there is no reason to take the pen apart to do that. Just unscrew the nib. A half a rice corn on a tooth pick does the trick or a Q-tip.

 

AC is right about the sac being cheaper than the piston. Soennecken, Kaweco, MB had to be dragged screaming and kicking into making piston pens by Pelikan.

Edited March 6, 2017 by Bo Bo Olson

[fly_us]

I started this thread because I thought maybe I'm missing out on better performance with a sac pen. I considered a modern Conklin with a sac. I have three piston Conklins now and they are quite good.

 

But my conclusion from all of your contributions is that sac pens don't function better than piston pens, and (of course) if the sac fails they are worse.

 

Best,

 

Alan

 

If the sac fails, they are super easy to fix. If the piston fails, well, good luck if you want DIY.

 

And because you want to buy modern Conklin, you shouldn't worry much about the filling system but the nib and the whole pen. I found that Conklin doesn't make the same quality as the vintage one. I bought 3 of them, one Mark Twain crescent filler, one Word gauge, one All American and all of them have trouble. May be i'm not lucky, but 3 out of 3 is really high probability.

[Jamesbeat]

I started this thread because I thought maybe I'm missing out on better performance with a sac pen. I considered a modern Conklin with a sac. I have three piston Conklins now and they are quite good.

 

But my conclusion from all of your contributions is that sac pens don't function better than piston pens, and (of course) if the sac fails they are worse.

 

Best,

 

Alan

If performance is your sole criterion then I suppose there isn't much difference, and maybe piston fillers are more convenient.

But opening your mind to lever and button fillers gives you a whole world of amazing vintage pens to try.

Don't be put off by the humble sac, it is still a valid filling mechanism and has given good service for a century already.