Rubber Sacs, Bulbs And Diaphragms

[tonybelding]

I'm gradually developing a strong distaste toward any pen with a rubber sac. I've just had too many problems with them. I'm beginning to understand why a "sac-less" design was such a big selling point back in the 1930s and 1940s.

 

I've seen "new old stock" pens that came with rubber sacs 40+ years old and worked Just Fine. I've also, unfortunately, seen brand new rubber sacs that failed after a relatively short period of light usage.

 

I've got a suspicion that some inks (i.e. some more than others) cause rubber to age and deteriorate.

 

I've got a suspicion that some sacs available today are not the greatest quality, and perhaps it may vary from batch to batch.

 

My latest mishap is a failing rubber bulb in my Edison Glenmont bulb-filler. It has't ruptured yet, but it has become limp and soft, and it has a small pimple-like swelling on the side of it. It clearly is in need of replacement. The pen is a few years old, and I don't think I've used it that hard.

 

One of my friends -- who does quite a bit more writing than I do -- has gone through multiple sacs in his Sheaffer Snorkel over the last few years.

 

I've had distressingly bad luck with my favorite pens lately. First I had two TWSBI Vac 700s which I loved in almost every way until they each suffered from (different) broken plastic parts. Now the Glenmont is letting me down. True, it's not a difficult or expensive fix, but... Are there not designs without this vulnerability?

 

Has the rubber sac outlived its time?

 

[WirsPlm]

The converter is the modern replacement for a sac (they function about the same), just sturdier and less prone to have materials problems. I think there's good reasons for why many vintage pens were sac pens, and for why those sacs have been left by the wayside as people have found better ways to manage the ink inside a pen.

[OcalaFlGuy]

P-51 Aero.

 

Just as is, it's still likely to outlive you.

 

Resac it Once with the new PliGlass sacs and you'll Make Sure Of That.

 

Bruce in Ocala, Fl

[balson]

i have not seen anyone talk about it here but its worth mentioning the oil from your hands is enough to break down rubber. i suspect that this might be part of the reason why newly installed sacs fail. bulb fillers would strike me as being especially prone to this.

 

washing your hands immediately before handling rubber is supposed to be enough to lower the risk, but i try and wear gloves when i remember. gloves are nice as well because shellac is hard to wash off.

[risingsun]

David Nishimura is selling his true silicone sacs in many sizes now... They may not be perfect, but if you're worried about the durability of latex sacs, these should help in that regard...

 

http://www.vintagepens.com/catill_nibs_parts.shtml#sacs

[OcalaFlGuy]

i have not seen anyone talk about it here but its worth mentioning the oil from your hands is enough to break down rubber. i suspect that this might be part of the reason why newly installed sacs fail. bulb fillers would strike me as being especially prone to this.

 

washing your hands immediately before handling rubber is supposed to be enough to lower the risk, but i try and wear gloves when i remember. gloves are nice as well because shellac is hard to wash off.

 

IMO, the biggest culprit for sac degradation is the ink you use in them.

 

I think it's generally understood by those who will admit the truth that some of the heavily saturated modern inks aren't good for latex.

 

IMO again, if you'll stick to the mostly mundane pen company inks your latex sacs will last long enough to not be a concern.

 

Or, be like me and others and use the saturated inks knowingly taking their risks.

 

PS; I'd think the talc would "take care of" most any finger oils left on the sac by a restorer in a lever fill pen.

 

Bruce in Ocala, Fl

[Dillo]

Hi,

 

In my pens, I use non-latex sacs, and intend to get some silicone sacs as soon as I have a new job to do.

 

I greatly prefer converters with sacs because the mechanism is generally more efficient with space than that of a piston converter. They also don't require the occasional lubrication needed by piston converters. Also, if the sac is translucent, one can check the ink level just as easily.

 

I'm still waiting for a more durable and long-lasting alternative to the latex vacumatic diaphragm. Once that comes out, I'll replace the diaphragm of the Parker that I keep in storage.

 

Dillon

Edited November 13, 2013 by Dillo

[BT-7274]

Hi,

 

In my pens, I use non-latex sacs, and intend to get some silicone sacs as soon as I have a new job to do.

 

I greatly prefer converters with sacs because the mechanism is generally more efficient with space than that of a piston converter. They also don't require the occasional lubrication needed by piston converters. Also, if the sac is translucent, one can check the ink level just as easily.

 

I'm still waiting for a more durable and long-lasting alternative to the latex vacumatic diaphragm. Once that comes out, I'll replace the diaphragm of the Parker that I keep in storage.

 

Dillon

One wonders if it'd be possible to make a vacumatic diaphragm out of pli-glass. Considering how much abuse the 51 aero sacs can stand up too, I'd bet that a pli-glass diaphragm would probably last at least 10-20 (maybe 30, but considering how much more stress it takes)years before it even started showing signs of strain. Of course, first, we need someone to test this out. I'd be more than willing to try this in my 51 vac, honestly.

[Dillo]

One wonders if it'd be possible to make a vacumatic diaphragm out of pli-glass. Considering how much abuse the 51 aero sacs can stand up too, I'd bet that a pli-glass diaphragm would probably last at least 10-20 (maybe 30, but considering how much more stress it takes)years before it even started showing signs of strain. Of course, first, we need someone to test this out. I'd be more than willing to try this in my 51 vac, honestly.

 

Probably not Pli-Glas aka PVC judging from the material itself and what a latex diaphragm is subjected to. I think silicone may work though, but it's hard to say.

 

Dillon

[balson]

 

IMO, the biggest culprit for sac degradation is the ink you use in them.

 

I think it's generally understood by those who will admit the truth that some of the heavily saturated modern inks aren't good for latex.

 

IMO again, if you'll stick to the mostly mundane pen company inks your latex sacs will last long enough to not be a concern.

 

Or, be like me and others and use the saturated inks knowingly taking their risks.

 

PS; I'd think the talc would "take care of" most any finger oils left on the sac by a restorer in a lever fill pen.

 

Bruce in Ocala, Fl

 

i have my suspicions about the modern highly saturated inks as well. it would be interesting to recreate Nathan's tin foil test but use modern sacs instead of tin foil to see if the inks really are eating through the sacks. i wonder sometimes if there is some sort of reaction going on between the old and new inks, possibly from changes in ph.

 

i am not sure i agree about the talc but i am no expert.

[Ron Z]

I wrote and posted an article about this on The Blue Fingers Blog. Each type of sac has it's strengths, each it's weaknesses. I believe that there has been a change in the composition of the latex used in sacs, and we're also seeing new super saturated inks that I firmly believe trigger the premature failure of latex sacs. It leaves some rather tough choices for the professional pen mechanic.

 

Dillo - a word of advice. If you start to use silicone sacs keep in mind that you must use silicone RTV to attach the sacs. They will not adhere to a sac nipple at all if you use shellac or any other adhesive. The only thing that silicone sticks to is silicone. Make sure that you use a non-corrosive RTV.

[Dillo]

I wrote and posted an article about this on The Blue Fingers Blog. Each type of sac has it's strengths, each it's weaknesses. I believe that there has been a change in the composition of the latex used in sacs, and we're also seeing new super saturated inks that I firmly believe trigger the premature failure of latex sacs. It leaves some rather tough choices for the professional pen mechanic.

 

Dillo - a word of advice. If you start to use silicone sacs keep in mind that you must use silicone RTV to attach the sacs. They will not adhere to a sac nipple at all if you use shellac or any other adhesive. The only thing that silicone sticks to is silicone. Make sure that you use a non-corrosive RTV.

 

Thanks for the heads up. I'm aware of the problems with sticking things to silicone. I've heard that Devcon 12045 is used by a few people. Is there anything specific you recommend? For some people who are wondering, some silicone RTV are acetoxy cure, and can cause corrosion.

 

Dillon

Edited November 13, 2013 by Dillo

[Ron Z]

Loctite 5040 is an alcoxy cure RTV, but it's about $35/tube. . It releases alcohol, which is the "solvent" found in shellac. You use very small amounts so that's not an issue - even if it were an issue.

[Paddler]

It's the ink. If you watch a sac fail in a desk pen, you will see the sac turn to goo at the nipple end where the ink sits all the time. The blind end will still be supple and new-looking. I had a sac fail in about a year and a half. It had only had one kind of ink in it. I poured the rest of that ink over the side and wrote its name at the top of my black list.

[Dillo]

Loctite 5040 is an alcoxy cure RTV, but it's about $35/tube. . It releases alcohol, which is the "solvent" found in shellac. You use very small amounts so that's not an issue - even if it were an issue.

 

I have on hand GE 5040 which is also alcoxy cure. Like the Loctite 5040, it releases methanol when curing. I haven't shipped any pens out of my shop using it since I'm still testing it. The general specification such as the shore etc seem identical from the data sheets I have on hand. Loctite is mil-spec.

 

My concern with the Loctite 5040 is that it doesn't have any mention of mildew protection. In my long term tests with silicone, silicone RTV without mildew-resistant additives that is in contact with fluids for long periods of time generally has a higher susceptibility to mildew. GE 5040 has mildew protection. My tests with GE 5040 indicate very strong adhesion, especially to plastics and glass. I'm still doing some other testing, but I haven't found a silicone RTV that sticks very strongly to rubber, especially softer rubber. I found that I can get a more adequate bond by treating the surface of the rubber with a thin coat of a polyurethane-based glue (not paint, this is glue), then using the silicone. While I'm aware that a very strong adhesion may not be completely necessary in a pen application, this is what my testing has shown so far. I'm definitely going to do some more tests.

 

Yes, ink contains biocides, but in my testing, these biocides aren't always enough to prevent mildew growth.

 

Also of note is that the alcohol used in the silicone in methanol which is not the same alcohol used in shellac. From my experience in chemistry, things dissolve differently in each solvent.

 

I continue to use shellac for latex sacs, but I have migrated to a different glue and treating method for PVC sacs that are attached to plastic parts to improve adhesion. The glue remains removable without any damage to the grip section, but doesn't come detached as easily as shellac. I have done extensive testing to the glue I use.

 

Dillon

Edited November 13, 2013 by Dillo

[Garageboy]

How badly does the use of RTV sealant damage the sac nipple?

Also, are pure 100% silicone sacs going to deprive me of any capacity? (In a Snorkel)

Edited November 13, 2013 by Garageboy

[rwilsonedn]

To reply to tonybelding's original question, yes, there are pens with no sensitivity to latex degradation, broken mechanical components, or any other failure mode I've ever seen. ED-fillers with modern feeds are bulletproof, and nearly immune to the blobbing problems of early (or traditional Indian) EDs. Pens like the Recife Crystal, most of the Deccan pens, or most any Indian vulcanite ED fitted with a Sheaffer NoNonsense feed are excellent examples. I don't have any experience with the Stipula Passaporto, but it might be another current example.

In addition to being nearly immune to failures, most of these pens have huge usable ink capacities.

ron

[Ernst Bitterman]

 

 

I'm still waiting for a more durable and long-lasting alternative to the latex vacumatic diaphragm. Once that comes out, I'll replace the diaphragm of the Parker that I keep in storage.

 

http://ravensmarch.files.wordpress.com/2013/11/dscn3066.jpg

 

Two of mine, and the one on the right is someone else's. I don't know how old that one is, but mine are both under five years old. All known to have been exposed to... a certain line of inks known for high saturations, which I'm now off in rubber-reservoir pens.

 

I've read Ron's blog entry, and have been pondering it and the above for a while, and I wonder if increasing amounts of ground-level ozone, as comes out of automobiles, might have some role in the phenomenon as well. But I'm still off that line of highly saturated ink.

[Dillo]

How badly does the use of RTV sealant damage the sac nipple?

Also, are pure 100% silicone sacs going to deprive me of any capacity? (In a Snorkel)

I don't have an answer for the first question, *yet*

For the second question, you shouldn't experience a capacity penalty in a Snorkel with a silicone sac.

 

Dillon