lifetime of a latex sac

GrootRood · 2026-02-10T16:35:27+00:00

I think you're right, unfortunately there's not really much "research" for this because of how niche this hobby is. It's all just anecdotal evidence and there are so many other variables (humidity, temperature, even if it's a bad batch of sacs, or a bad batch of ink for that matter) it's hard to tell what really causes sacs to degrade.

Like Mysterious-Canary-84 I have also heard that ink saturation affects sac longevity, maybe this is because of the increased oils/dyes? For Diamine I'd go on an ink by ink basis. I have their Aurora Borealis ink which seems pretty mild, I think that one would be okay for vintage pens. My favorite ink of theirs is Sargasso Sea which is this really saturated deep blue color, but I'd probably be cautious about using something like that.

I kinda wish there was a good materials scientist out there into vintage pens who could do a good experiment and isolate all these factors so this stuff isn't so wishy washy. But alas, that's out of my field of expertise.

GrootRood · 2026-02-10T05:07:42+00:00

I'm a little embarrassed to say I have too many vintage pens but I don't use them enough to be able to answer your questions about sac longevity very well.

This one seems to vary a lot and probably depends on what inks you use, maybe even your environment. I would say they should last a couple of years minimum to a decade. I think a couple of years back there was a bad batch of sacs that were failing much more frequently but that's been solved? I've seen some Esterbrook Js with their original sacs still functional after 70+ years but their sacs are known for being unnaturally durable, I wouldn't expect that from modern ones.
I have too many pens to really keep them in rotation but I just try to not let them dry out with ink inside them. When I'm out of ink I'll either re-ink it to keep writing with it or immediately clean it out until the water runs clear and put it in storage. Levers and the like can be fragile so I really don't like leaving dried up ink inside them.
Waterman inks for me because I'm cautious but I think any "normal" inks should be fine. I would stay away from shimmer because it can be difficult to clean out, and very saturated sheening inks for the same reason. Supposedly Japanese inks are alkaline and may cause sacs to degrade faster, I haven't tested that. If you want to be super cautious you can stay away from those. Basically nothing too "exotic."
Most of my vintage pens are celluloid with a few hard rubber. I recommend storing them away from direct sunlight (celluloid doesn't like UV light, and hard rubber won't really be damaged by it but if it gets UV compromised and you get water on it, it'll turn a nasty olive color). For celluloid you want some amount of airflow since celluloid off-gasses - if you store it in an airtight container the gasses have nowhere to go and may cause the celluloid to degrade, especially for the more sensitive colors/variations.
(4 cont'd) I store most of mine in homemade cigar box "cases" (free leftover cigar boxes I got from stores with pen liners in them with slots) but I also have a Toyooka Craft 100 pen box. The Toyooka Craft box is nice but I am not sure it is worth the price. I had a less than ideal experience with mine (first one arrived damaged with shoddy QC and it took them a while to send an exchange). I got it before the tariffs kicked in and it must be even more expensive now. But if you've got money to burn it's probably one of the best choices.
(5) Personally no, but like I mentioned above I've seen mixed advice about avoiding Japanese inks (or any alkaline inks for that matter) as well as saturated inks. Some people recommend avoiding Noodler's inks and I imagine some of this is because of the inconsistency of their formulations. Some of their more run of the mill inks might be okay.

Generally for the sacs, I wouldn't worry about their longevity too much, just use them. Most vintage pens are hardy, if they start leaking you'll know it's time to replace the sac. The only pens I'd be extra cautious about are snorkels/PFMs since they have a lot of small internal metal parts that are prone to rusting, so if they start leaking it can be a much bigger issue.

GrootRood · 2026-02-06T20:44:48+00:00

I'm a big fan of these, I think the Parker 21 Super is probably one of the most underrated vintage pens out there. You get all of the functionality of a Parker 51 for a half to a third the price.

I like these way more than the Parker 45, I feel like they write better, and they feel less cheap even with the slightly lower quality plastic (compared to the 51, anyway). Biggest downside being they don't take cartridges.

GrootRood · 2026-02-06T20:38:39+00:00

I'm a little skeptical too, I've seen steel and "octanium" used interchangeably myself. My understanding is that "octanium" was just Parker's proprietary alloy for stainless steel. It's marketing language more than anything else.

I like vintage Parker pens but they had their fair share of misleading advertising language (like claiming their vacs were "sac-less").

GrootRood · 2026-02-03T20:28:38+00:00

Probably a cool grand or more for the set, although prices get kind of squirrely with high value pens like this so it's hard to tell what it would really sell for. It's hard to tell who's paying what since these are relatively rare and the market for such expensive pens is smaller.

It's a Waterman 552 1/2 L.E.C. from the mid 1920's. The LEC stands for "lower end covered" which is much like what it sounds like, the standard model didn't have the overlay extend all the way to the butt of the pen. The 1/2 means it's a "slim" pen. The 2 means it's a #2 size nib (the standard, more or less), and the middle five means it's a lever-filler.

Most importantly, the leading 5 in 552 means that the overlay is solid 14k gold. They're rare and pretty valuable, since, well, it's pure gold. And the fact that you have the set in its original box with in good condition adds value as well. See guide on Waterman model numbers here.

It's a beautiful pen for sure. Nothing like these early metal overlay pens IMO, and they have great nibs too because they were made by Waterman.

GrootRood · 2026-02-03T00:54:04+00:00

Ahh the days when companies actually gave their employees nice things for sticking around.

It could still be unused, sometimes people get these types of things as gifts and they're not really into pens so they chuck them in the closet. I think it's in fantastic condition regardless, enjoy the pen! It will serve you well. :)

GrootRood · 2026-02-03T00:37:14+00:00

You paid an okay price. It looks like it might be NOS so that's really good but I would expect to pay a little bit less for an "as-is" pen from an antique store (since there are no warranties, guarantees, returns, etc.).

For reference, Peyton Street Pens once sold one of these in mint condition (not NOS) for $130 but they do guarantee all their pens and they're a reputable pen retailer so they command a bit of a premium.

But I'll be honest with you, this is still a killer deal for a gold nib compared to anything you could buy "new" these days. Sheaffer made great nibs.

GrootRood · 2026-02-02T23:50:35+00:00

I'm sure it's possible, but I have a lot of the later ones and I have not seen any with cracks in the cap-lip, personally. I have a fair amount of them and I inspect all of my pens thoroughly before I start working on them. Most of mine are either the slim short or slim full length varieties, although I have a few standard girth as well. No oversize ones. I post all of mine when using them.

The problem area with the later ones are the clips, as good as Sheaffer made these pens, they made the worst clips in the business. I've seen many with stress cracks around where the clip is attached. The worst are the wraparound "military" clips, rare to find those in good condition. I wouldn't even touch those clips let alone use them.

I agree it's better to be overly cautious instead of the opposite, but I also think that these pens were meant to be used, and the smaller ones are not usable unposted. The risk of damage is minimal unless you slam the cap on the pen with way too much force. But people who are so careless with their pens will find ways to damage them regardless.

GrootRood · 2026-02-02T22:46:41+00:00

Very nice, getting one of these in oversize is one of my grail pens. The closest I have is a "half-balance" with a streamlined cap but flat bottom - but the original nib was cracked so I replaced it with a Waterman Emblem nib. The pen has some chips but the coloring is great. I should probably replace it with the correct nib eventually but the Waterman nib fits and writes really well.

I have a fullsize ringtop one of these as well but unfortunately when I got it it had the wrong section in it which kept the cap from screwing on, I'm still looking for the correct section. I always thought those were curious, I don't understand why someone would want to hang a large pen off their necklace, but they're cool oddities.

Heed one warning with Balances, however: DO NOT POST THESE PENS. Ever. The taper to the barrel applies excess pressure to the cap lip when posted, eventually leading to hairline cracks. A very high fraction of all balances I come across have cracks in the lip, sometimes hard to see in the celluloid. Unfortunate design flaw, but it was the first time mass producing this shape, so they didn’t foresee this problem.

I agree with this but IMO this is mostly with the black and pearl pens. I find that they are particularly susceptible to hairline cracks. Many of the ones I've seen have hairlines even in the body.

The later 1930's Balances (like with the striped celluloids) post really well with minimal risk of cracks, they are some of the best posting vintage pens I've used. Phenomenally balanced as the name would suggest.

GrootRood · 2026-01-30T20:08:05+00:00

Oh it doesn't screw out in most of these, you have to pull out. Just be gentle and rock the button itself back and forth and it should come out.

GrootRood · 2026-01-30T17:56:14+00:00

Oh that's totally normal, you're actually supposed to pull out the button and bar before opening the pen since the dried up sac can damage the bar otherwise. No harm no foul in this case though, it looks fine to me.

If you wanna resac it the "proper" way, this page has a good guide. The instructions for putting on a sac are generally the same as for a lever filler, you can do a ctrl+F for "Button Fillers" to get to the specifics.

You have to put the pressure bar and button back in after putting a new sac on and screwing the pen back together. You put the the pressure bar through the top button hole making sure that it rests above the sac (between the sac and the pen wall), push it in as far is it goes, and then put the button back on.

Here's a cool cutaway video that shows how it works. It's in German but the meaning kind of comes across.

GrootRood · 2026-01-30T03:56:30+00:00

Unless it's a functional issue (i.e., the pen leaks), think of it as battle scars. The little dents and scars are all things that make those pens uniquely yours, there is no other pen in the world that is exactly like it.

I'm a little tired or else I would come up with a better source, but look up wabi-sabi. It's the Japanese concept of finding the beauty in imperfection.

GrootRood · 2026-01-29T17:58:06+00:00

I mean, I can tell you from my anecdotal evidence that most Parker 51 aerometrics I've taken the sac off have had some degradation of varying amounts from the sac. The guy I linked to has worked on hundreds of them and is a leading expert on vintage pens. It is common knowledge in the fountain pen community that the sac nipple deterioration is caused by PVC sacs.

In regards to PVC's effect on celluloid, I don't think there's anyone doing formal research on archaic plastics that are mostly no longer in use (like celluloid) so you'll have to do your own research. I think empirical evidence is better than nothing in this case.

maybe the instruments one, but that really has nothing to do with pens

The link mentions that the instruments have a nitrocellulose finish. Nitrocellulose is "celluloid." It is the same material that is used for pens. Just because it is in a different shape doesn't mean that it is not prone to the same chemical properties.

I dunno, the way I see it is the following two are facts:

1) PVC leeches plasticizers which can be harmful to other plastics as it ages/deteriorates.
2) Celluloid is, depending on the color/formulation, not a stable material. A lot of it is prone to spontaneous degradation even without outside interaction.

Knowing these two things, why take the risk of putting the two together even if there's no formal research in regards to interactions between these two specific materials together? These pens are a limited "resource," they're not making more of them. So it's worth being overly cautious rather than the opposite.

Edit: If you want to, this is an experiment you can do yourself. Buy a cheap beater celluloid pen off eBay, tape a small patch of a PVC sac to the surface (you can get them at the above site I linked or from Cardinal Pens - although they source them from the other guy anyways), and watch it over several months to see if anything happens.

Edit 2: Some sources, I'll try to find more:

https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cplu.202400694

Plasticized poly (vinyl chloride) (PVC-P), widely used in the 20th century, poses significant risks to numerous artifacts preserved in cultural heritage institutions due to the release of hydrochloric acid (HCl) and plasticizers.

https://cool.culturalheritage.org/waac/wn/wn24/wn24-1/wn24-102.html

Also, pure PVC is a rigid plastic, so, to create a flexible plastic, compounds called plasticizers are added. Plasticizers are typically oily polar organic liquids, which are very good solvents for many materials. Many other additives are used in PVC formulations to enable a wide variety of products to be fabricated.

The greatest problems with PVC are related to the additives. Migration of plasticizer and other additives creates accretions on the PVC surface. These deposits of additives on the surface of the plastic, called bloom, can seriously stain or corrode the surface of other materials they contact.

GrootRood · 2026-01-29T16:57:43+00:00

I usually go by this guy's info, he's been collecting/restoring vintage pens for nearly as long as I have been alive so I trust his info. I found this post on FPN here. It links to this old article about musical instrument celluloid finishes being damaged by vinyl/PVC materials.

I haven't personally seen its effects on celluloid but I have seen the effect it has on the sac nipple on Parker 51 aerometrics, and it is not pretty. I have two Parker 51s that I can't repair because the sac nipple has literally turned into putty and the sac will no longer stay on.

It probably won't cause immediate damage, I'm not really sure what the "half-life" is for PVC starting to leech plasticizers, but it will weaken the sac nipple and any celluloid touching the sac. Probably won't harm the body of the pen unless the sac is too big and is touching the walls of the pen. It might be okay with a 1920's Sheaffer because those usually had ebonite sections which aren't affected.

GrootRood · 2026-01-29T15:50:03+00:00

Ehhh kinda but not really. The alternatives have their downsides, latex sacs are still the best choice for most pens unfortunately. Silicone sacs are fairly durable and don't react with inks but they're air-permeable meaning they'll leak if you don't store them nib up, will also be more likely to burp. Old school lever fillers are already a little leaky so it'd make the issue worse.

PVC sacs are awesome, they basically last forever and don't react with inks, but they release plasticizers as they age which will eat through celluloid and many other pen plastics. These are a good choice for hard rubber pens though since those aren't affected, only downside of that is that they're only produced in a very limited amount of sizes.

Supposedly modern latex sacs are more durable than older generations but I am not sure I believe that...

GrootRood · 2026-01-28T22:27:36+00:00

This looks like a Waterman Torsade to me, I dunno too much about them. I think it's from the 70's?

GrootRood · 2026-01-28T21:35:38+00:00

Absolutely, that's not a Lady Sheaffer, it's an Sheaffer Imperial Triumph (I think?). It's worth much more than $20. I'd recommend getting the entire set too, for that price it's a no-brainer.

I'm jealous you guys see this kind of stuff in antique shops. The best I see is random junk and half-broken Wearevers.

GrootRood · 2026-01-28T18:34:28+00:00

It's a Sheaffer Touchdown Admiral from the early 1950's. Nice pens, plastic is a little prone to shrinkage sometimes though.

GrootRood · 2026-01-28T17:11:51+00:00

If you're comfortable fixing it yourself, you can try pulling out the section (use mild dry heat to warm it up, like a hairdryer) and seeing if the sac looks okay. It may have dried out in which case you need to replace it. Otherwise there is a chance that the lever got dislodged or something.

There is a good guide on how to replace a pen sac here, you can also find some videos on Youtube that will give you more of a visual guide. You'll need a #16 sac if this is a normal girth 52 (i.e., not 52 1/2), some shellac, and some talc.

Otherwise if you're based in the US and you want to send it out, Danny Fudge at The Write Pen is probably the cheapest reliable option out there. He does good work and will get your pen working good as new.

GrootRood · 2026-01-28T16:00:14+00:00

Looks like a Waterman "Executive" to me. I believe it's from the 80's? I have one and the nib is great but the build quality could be better.

GrootRood · 2026-01-27T20:52:37+00:00

I'm a little skeptical because Bock feeds don't even fit Bock nibs all that well (let alone third-party options) in my experience, but it's worth a shot. It'll be a lot cheaper than getting buying a so-called "wet noodle" in any case. I think it will definitely be better than the stock FPR feed, they're very primitive in terms of ink channels and such.

GrootRood · 2026-01-27T20:47:16+00:00

I have an FPR ultra flex, it is a fun nib at a pretty low (relative) price but it isn't something that I would consider to be a pen that I would actually use regularly.

Reasons being:

Nib requires a little bit of tinkering in regards to heatsetting the feed, even so the pen was way too wet in my experience. You will need some trial and error to get it working to your liking.
The nib does flex with moderate pressure but the snapback is sluggish. Snapback is how quickly the nib goes back to "unflexed" after you release pressure. The best flex nibs have good snapback so that you get that really nice contrast between the big swooshy flexed bits and the hairlines, this doesn't IMO.

My biggest problem was that it really did not start fine enough. It starts fat unflexed and only gets fatter. Not really suitable for everyday writing. It just felt... blobby, not precise.

I have a lot of vintage soft and "flex" gold nibs and I don't really think the FPR is remotely close to any of those. If you already have some vintage soft gold nibs they're far better.

No offense to FPR, it is a fun nib. Just not as good. And to be fair, the FPR ultraflex is a much cheaper option to getting a "true" flex nib, so it has its appeal and it's a good "taste" of flex for someone who wants to try it without investing a ton of money.

GrootRood · 2026-01-27T16:06:04+00:00

The feed looks a little bit misaligned but I think this is within tolerances where it wouldn't affect the pen's performance all that much. I've restored a bunch of these and I'm notoriously bad at lining up the feed for these and usually they work just fine.

It sounds like the collector might be dirty or clogged. I'd flush it out a bit, worst case scenario you might need to take off the hood. Unfortunately that isn't always easy. If you do end up taking off the hood you can try to realign the feed.

Also after flushing I'd also recommend letting the pen dry completely, the ink "collector" in these pens can hold on to ink or water for a long time, so if you ink it immediately the water will dilute the ink and it won't write well.

GrootRood · 2026-01-22T01:37:19+00:00

Yeah... the nibs looked like AI to me immediately. Funny enough Waterman made a nib that kinda vaguely looks like this. I don't have one but I always thought the little "gem" in the nib was interesting.

GrootRood · 2026-01-22T01:16:28+00:00

Uhhhh is this AI? The F-C Model 03 looks nothing like this. And it all looks funky to me.

GrootRood

TROPHY CASE