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Thread: Pen sacs materials

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    Default Pen sacs materials

    Good morning everyone! I've always used 'rubber' sacs. On one of my pens I have used a silicon sac which I'm now in the process of replacing hoping the pen will stop leaking. Asking around I've been told that silicon sacs are inert as they do not release toxic gases that can ruin old vintage pen bodies and so are to be preferred. 'rubber' sacs on the other hand release toxic gases that ruin vintage pens. I can't believe this. In the year 2000 we haven't found a way to produce non toxic rubber sacs? How long would it take for this toxic fumes to ruin a celluloid, ebonite or whatever pen, 10, 20, 50 years of continuous usage? Is this simply a myth? Are there studies out there that actually proof this? thank you. Marco

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    Default Re: Pen sacs materials

    Certainly not a myth, Marco. Certain colours of celluloid - jade for instance - are badly affected by the deterioration of latex sacs. Hard rubber pens are not affected. The outgassing isn't toxic in the normal sense of the word. Sulphur is a required component of the sacs and it is its release during the decomposition of the sacs that attacks celluloid. The clear sacs are not without problems of their own. They're stiffer than latex and may stress pens. I use silicone (not silicon) sacs for pens that are likely to be affected by discolouration but latex for everything else. I've seen it suggested that components of ink and hard rubber inner caps may play a part in discolouration.

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    Default Re: Pen sacs materials

    eachan thank you for your insight and spelling correction. the two spellings mean two different things, now I know. Celluloid greens and blues only then can change colours due to this chemical reaction or other colours too? At a glance how do you tell celluloid from BHR or from plastic?
    Sparkly colours are not BHR I guess. Can the year of production have a play in this?
    Thank you
    Marco

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    Default Re: Pen sacs materials

    I'm not really the person to make a list of all celluloids affected by this form of deterioration because it isn't seen so much in my area of interest (British pens) as it can be elsewhere. Mixed colour celluloid is less affected, I think, though not entirely clear of it. I see it most in jade and lapis lazuli. Best way to tell hard rubber is to rub and sniff. The rubbery smell is unmistakeable. Telling the difference between celluloid and plastics is difficult. The year of production can help but mystery materials are around quite early. For instance Mabie Todd was using a material that fails the tests for celluloid in the 1930s.

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    Senior Member Jon Szanto's Avatar
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    Default Re: Pen sacs materials

    Marco, this IS a well-known and documented aspect of pen making and history. Eachan has very well described all of the basics, the reason for the "off-gassing" (which is the term I think is most often used) from the sulfer in the rubber, and other items.

    A black pen will likely show no effects of this but, as mentioned, some of the colored celluloid can be affected to varying degrees. Of the colors I am aware of, Jade (one of the earliest color pens) can go quite dark, the early blue/"Lapic" pens are hard to find without darkening. Much lighter colors, like the Parker "Black and Bearl" and the many pens, including Sheaffer black-and-white mixes are very prone to discoloration. These latter are easy to spot as the white/cream portions turn from a very light color to a gradually tarkening tan/brown. It isn't always the end of the world aesthetically, if the change is somewhat uniform, but often you will get areas of the pen that turn and others that don't. Usually, as in that Parker example, you'll see a barrel much darker than the cap:


    Photo from Tony Fishier's Parker Collector site

    In the following photo are some of my Sheaffer OS Balances. Note that pen #3 and #5 are made from the same material, but the first has significant discoloring, while the latter is in near original condition (judging by catalogs of the time). This pen has a silicone sac and is stored away from the other pens to keep the color good:


    All of the is just known fact and an unfortunate aspect of old items. As stated earlier, there is much documentation about the issues and the ways to combat it. I would urge you to look at the short article "Discoloration and It's Causes" by David Nishimura on his site. There are many other similar items scattered around.

    We do what we can to preserve. As mentioned, removing rubber sacs and replacing with silicone may bring other problems (for a user) but do avoid the off-gassing. Other routes are having plenty of air circulations, and even chemically treated papers that counteract the acidic vapors can be used in the storage areas. I'm in the process of making up a new pen storage area that incorporated both of those facets.

    Hope this helped.
    Last edited by Jon Szanto; February 6th, 2022 at 12:27 PM. Reason: Fixed external link
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    Default Re: Pen sacs materials

    Quote Originally Posted by Jon Szanto View Post
    ...#5....
    Is No. 5's barrel machined from a rod or from a formed sheet (with the seam down the side)?

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    Default Re: Pen sacs materials

    Quote Originally Posted by FredRydr View Post
    Quote Originally Posted by Jon Szanto View Post
    ...#5....
    Is No. 5's barrel machined from a rod or from a formed sheet (with the seam down the side)?
    Sheet (seam on both barrel and cap). And for you I cleared off the desk to get to the place where it is stored just to verify that!
    "When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
    and that when Truth and Error have fair Play, the former is always an overmatch for the latter."

    ~ Benjamin Franklin

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    Default Re: Pen sacs materials

    Hi John, this is all very well and interesting and thank you for the link. Nishimura in his article at the end says 'the old sacs are the ones that are most dangerous'. Old compared to what? I buy a sac today and in 3 years time is considered old and this is dangerous? 5 years? Old referred to a sac that has been in the pen for 20-50 years and is now a solid piece of gunk?
    So I sit on the fence and wait for more proofs if and when they became available. Sorry 😊

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    Default Re: Pen sacs materials

    Quote Originally Posted by MarcoA64 View Post
    Hi John, this is all very well and interesting and thank you for the link. Nishimura in his article at the end says 'the old sacs are the ones that are most dangerous'. Old compared to what? I buy a sac today and in 3 years time is considered old and this is dangerous? 5 years? Old referred to a sac that has been in the pen for 20-50 years and is now a solid piece of gunk?
    So I sit on the fence and wait for more proofs if and when they became available. Sorry 😊
    You seem to want exactitude that no one can provide. I know of no pen people that have done tests on modern sacs to gauge the degree and speed of off-gassing. There are only one, maybe two makers of pen sacs today since it has become an ultra-niche item.

    The main point is simply that in times past, when sac pens were prevalent, certain celluloid could and did react with off-gassing from rubber sacs. Not all pens did it to the same degree, even in the same celluloid. Differences could be the variation in sac manufacture or batches of celluloid. Additionally, how a pen has been stored can very much affect how these elements play out

    Your questions very likely will NEVER be answered to your satisfaction. These are the basic facts and details that have fallen out after decades of pen manufacture, use, collecting, storage, and observation. We do have materials today that can be used in pens made of materials known to have issues with discoloration, and can mitigate any change; pens that are not prone to change can still be re-sacced with the latex sacs.

    Enjoy your time on the fence. That is entirely your choice.
    Last edited by Jon Szanto; February 6th, 2022 at 01:41 PM.
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    Default Re: Pen sacs materials

    Quote Originally Posted by Jon Szanto View Post
    Quote Originally Posted by FredRydr View Post
    Quote Originally Posted by Jon Szanto View Post
    ...#5....
    Is No. 5's barrel machined from a rod or from a formed sheet (with the seam down the side)?
    Sheet (seam on both barrel and cap). And for you I cleared off the desk to get to the place where it is stored just to verify that!
    Thank you, Jon!

    The nicest examples of '30s Sheaffer black & pearl that I find these days will have that seam, and they're far less common. I've wondered if celluloid sheets are more impervious. Could it be a function of how they were extruded or a change in the ingredients? Or my imagination?

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    Default Re: Pen sacs materials

    Quote Originally Posted by FredRydr View Post
    Quote Originally Posted by Jon Szanto View Post
    Quote Originally Posted by FredRydr View Post
    Quote Originally Posted by Jon Szanto View Post
    ...#5....
    Is No. 5's barrel machined from a rod or from a formed sheet (with the seam down the side)?
    Sheet (seam on both barrel and cap). And for you I cleared off the desk to get to the place where it is stored just to verify that!
    Thank you, Jon!

    The nicest examples of '30s Sheaffer black & pearl that I find these days will have that seam, and they're far less common. I've wondered if celluloid sheets are more impervious. Could it be a function of how they were extruded or a change in the ingredients? Or my imagination?
    It's hard to say, Fred, so many variables. I just took a quick look (would have to shoot photo later) of another that came in a set, it has the seam but has more change in the white than the one shown above, though nowhere near as badly discolored as other examples.

    ETA: I just took out a barrel (with a broken cap) and a better pen I use regularly in this color, both of them very darkened to caramel and black. Both of those are non-seamed material. Maybe the sheet celluloid was a better formula with regard to discoloration? All we need now is to find a pristine example without a seam to completely mess up new-fount theories!
    Last edited by Jon Szanto; February 6th, 2022 at 02:40 PM.
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    Default Re: Pen sacs materials

    Quote Originally Posted by Jon Szanto View Post
    ...All we need now is to find a pristine example without a seam to completely mess up new-fount theories!
    Those have been locked away in collections by those who started collecting before I did.

    Here's a late flattop that was formed from sheets (that was available to me but I didn't buy). Below that is my '29 Balance machined from a rod. There is a tiny spot of discoloration, but it is in the cap where the feed would be (i.e. ink), not the sac.

    IMG_4744.jpeg

    DSC01235.jpeg
    Last edited by FredRydr; February 6th, 2022 at 04:01 PM.

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    Default Re: Pen sacs materials

    Can we draw inferences from these examples? It certainly adds to the consideration of environment and storage conditions wrt the effect on the pen from the gasses.
    "When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
    and that when Truth and Error have fair Play, the former is always an overmatch for the latter."

    ~ Benjamin Franklin

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    Default Re: Pen sacs materials

    I've been doing a bit of reading on rubber and off-gassing. Every rubber made item emits these gasses. Some for a limited time some for years. Ventilation is encouraged to get it dispersed quickly. Relating it to fps there isn't much out there that I have found, yet. It is a bit like the famous WMD of old 🙄

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    Default Re: Pen sacs materials

    Another example of darkening-

    Many Parker Vacumatics were made of clear and colored laminated celluloid in "stripes." The clear celluloid was to allow you to view the ink level in the pen.

    Most Vacumatics today are seen with varying degrees of darkening in the clear sections. Some are essentially black while others are as clear as made, and most are somewhere in-between those two extremes.

    If one has a very clear one, some recommend removing the diaphragm completely so as to avoid the potential for off gassing rubber darkening the pen.

    Personally, I just take my chances with high clarity ones(and my really good ones are common colors/types) as I don't want a pen that I can't use and Vacumatics are some of my favorite writers.

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    Default Re: Pen sacs materials

    re. sacs darkening pens. Peter Amis of the Pen Sac Co says that the modern sacs will not outgass and darken celluloid like the vintage sacs did. He would know what the differences between vintage and modern latex formulations are that allow him to say that with confidence.

    But there is the problem if latex failing over time, and being attacked by dyes. Silicone sacs are gas permeable, so the pens ooze. PVC sacs have their own issues.

    My article about this can be found here.

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    Default Re: Pen sacs materials

    Hi Ron, so today sacs that do not have off-gassing issues can be made. This was my question and now there is a statement from a producer. Great!!

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    Default Re: Pen sacs materials

    This is a bit off the topic, but in the same ballpark I have a c.1925 Jade Flattop that looks dark on the barrel, especially where it joins the section, while the cap is faded and yellowed.



    What might cause that?

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