10 ms·

What Is the Transparent Material at the End of a Gel Pen Refill?

144 points by thomas 5y ago

EricE 5y ago
Nothing beats a Fisher Space Pen!
- GloriousKoji 5y ago
  I can attest to that. When I was a boy my parents gifted me a Cap-O-Matic space pen. It's a fairly generic looking pen with a small space shuttle logo in the middle of it but uses their patented pressurized ink cartridges. Of course like any boy I took it to school to show it off and use it until someone tried to steal it. It was super precious to me at the time so I stored it away in my precious items tin lunch box under my bed. It stat there for a couple of decades, forgotten through time. Like any well prepared person I keep a pen in the glove box of my car. The problem is they last only a couple of years before they leak or dry out which means they never work when I actually need them. One day I'm back home with my parents and I find my old tin and the Fisher space pen in it. It still worked perfectly and I figured if it's suppose to handle the rigors of space then a car glove box shouldn't be a problem. It wasn't. After about a decade in the glovebox of my old car it found its way to the glove box of my new car (which I guess is kinda old when compared to a car from today). It still works perfectly.
  - mc32 5y ago
    That's a pretty awesome story to share. I may have to go find the one I was given many years ago too.
  - Johnny555 5y ago
    The problem is they last only a couple of years before they leak or dry out which means they never work when I actually need them Of course, the other solution to this problem is just as in the apocryphal story [1] about the origins of the space pen... use a pencil instead. I keep a couple pencils and a $2 sharpener in the car. Of course, there are some situations where a pencil is not ideal (like writing a check), but if you really need to write something, it's always going to work. [1] https://www.scientificamerican.com/article/fact-or-fiction-nasa-spen/ https://www.scientificamerican.com/article/fact-or-fiction-n... https://www.snopes.com/fact-check/the-write-stuff/ https://www.snopes.com/fact-check/the-write-stuff/
    - taneq 5y ago
      Yeah, but... space pen!
    - gumby 5y ago
      I just use my pocket knife to sharpen pencils, but I live where it is legal to carry one.
      - eru 5y ago
        Aren't pocket knifes legal in most places? (I assume you mean some swiss army style folding knife?) Most because that kind of folding knife that doesn't lock in place would be less useful in a fight than leaving the knife folded and wrapping your hand around it as a weight.
      - irrational 5y ago
        Other than a place like an airplane, where is it illegal to carry a pocket knife?
        ehvatum 5y ago
        UK, I imagine.
        agurk 5y ago
        Penknives are allowed to be carried without needing a justification in the UK. > It’s illegal to [...] carry a knife in public without good reason, unless it has a folding blade with a cutting edge 3 inches long or less [0] It also cannot be locking to not need a good reason to carry it. This is set in case law not the text of the relevant laws (and could could also probably be overturned if anyone had the time, money and inclination to challenge it). [0] https://www.gov.uk/buying-carrying-knives https://www.gov.uk/buying-carrying-knives
        deleted 5y ago
        [deleted]
  - mike_d 5y ago
    > The problem is they last only a couple of years before they leak or dry out Are you not following proper protocol of swapping out for new pens between space missions?
- powersurge360 5y ago
  You (and others) might be pleased to know that you can get the space pen as a Parker refill that fits many different pen bodies. You can also get the very popular uni jet stream ink in the same refill type. I suggest a Kaweco sport as the pen body of choice
  - c22 5y ago
    Thanks for this tip. I used to carry a space pen regularly but its small size and shape would slip out of my pockets and I would routinely find myself having to replace them.
bernulli 5y ago
“Gel ink is viscous, but it’s not thick enough to prevent it from flowing. This means it can evaporate over time” These are three different, unrelated phenomena. In a Newtonian fluid, no matter how large the viscosity, the fluid will flow when a shear stress is applied (think honey). A gel is instead typically a non-Newtonian fluid, i.e. a certain threshold stress has to be reached before motion sets in (think toothpaste). I don’t really see why the author then relates evaporation to viscosity. Shielding the fluid of interest from mixing with the surroundings will prevent evaporation (close the bottle of water and it will remain full, leave it open and then it will evaporate eventually).
- andreareina 5y ago
  > (think honey) or even pitch: https://en.wikipedia.org/wiki/Pitch_drop_experiment https://en.wikipedia.org/wiki/Pitch_drop_experiment
  - bernulli 5y ago
    My favorite least exciting experiment!
- aqme28 5y ago
  > Shielding the fluid of interest from mixing with the surroundings will prevent evaporation (close the bottle of water and it will remain full, leave it open and then it will evaporate eventually). If you close the other end, pressure will prevent the ink from flowing out the tip.
  - bernulli 5y ago
    Maybe, if it’s not about a bottle of water where we don’t want anything to flow out, one could use some sort of Transparent Material At The End Of A Gel Pen Refill to close the plastic pipe and prevent exposure to air to prevent evaporation!
  - zaarn 5y ago
    There is gas pressure pens that have a small amount of pressurize inert gas at the end instead, which means that those are in fact closed on the end and operate much longer due to no evaporation issues.
throw_away 5y ago
Oh wow. Did not know that there was an ISO standard for pen refills: https://unsharpen.com/pen-refill-guide/ https://unsharpen.com/pen-refill-guide/
- gumby 5y ago
  But not fountain pen cartridges (the “international format” seems not to be an ISO standard). However there are ISO standards for the inks themselves, which can be the contents of these cartridges. Unsurprisingly there are also national ink standards. For example certain contracts like marriage licenses in Germany are only legal if signed with one of two DIN standard inks that are certified to last at least a century.
  - mschuster91 5y ago
    > For example certain contracts like marriage licenses in Germany are only legal if signed with one of two DIN standard inks that are certified to last at least a century. German here. WTF? (Not that I don't believe it, but I couldn't find sources for that one)
    - richlogan 5y ago
      This is Iron Gall Ink I think - we have registrar ink here in the UK too. https://en.wikipedia.org/wiki/Iron_gall_ink https://en.wikipedia.org/wiki/Iron_gall_ink
      - wl 5y ago
        Iron gall ink is a poor choice for documents that should last a long time. It's an acidic ink, which damages paper. The iron rusts over time. The ink blooms. These things are manageable if the documents in question are stored in a cool, dry place. But why bother when there are better inks today?
    - mhd 5y ago
      I don't know about any special rules for marriage licenses, but for inks there's DIN/ISO 12757-2. Search for "Dokumentenechtheit". It's not that exotic, though. It gets a bit weird for printers. Laser and dot-matrix printers generally are okay, but you need a certified ink jet. Problem is that by the time they're certified, they might not be available. And then you only get the certification on proper paper, with the default inks, so don't cheap out on your old HP... As this is a ISO norm, too, I don't think this is something peculiar to Germany, after all, document storage isn't just a teutonic issue.
tryonenow 5y ago
They didn't really indicate why the end is sealed with a fluid as opposed to something physical. I suspect it's because flowing ink with a solid stopper would create a vacuum and quickly cease to function. A stopper is fluid and so can flow along with the ink. The space between the stopper and the shell is probably vented.
- computator 5y ago
  Yes, it's such an obvious question that's not addressed in the article. I was thinking about why they don't pinch the plastic tube closed at the point where the ink stops being filled. The following statement in one of the patents[1] seems to confirm your explanation: The aims of the arts are to make the ink follower follow the ink smoothly. [1] https://patents.google.com/patent/EP1002663A1/en https://patents.google.com/patent/EP1002663A1/en
- ExtraE 5y ago
  Not vented so much as just not air tight-- no reason to make it air tight, and the inside of the pen is by no means sealed, as you can tell if you've ever taken one apart (or had it explode inside your bag). The parts just don't fit that well together. Which I guess is a vent in a sense, although that's probably not the main design consideration. The (obvious) exception being the space pens, which do have some pressure chambers. They solve the vacuum issue by being pressurized, which has the nice benefit of letting them write upside down. I imagine they've made it viscous/non-Newtonian/whatever (not sure on the technical fluid mechanics term) enough such that gravity pushes/pulls it down towards the tip but prevents it from flowing the other way. Edit 1 (just before getting in the shower): Removed references to air pressure, as I don't think that makes a difference. Edit 2 (post shower): Air pressure might a difference after all, it depends on where the seal is. If there's an air tight seal on the tip end (which there might be, if that's how it's kept from leaking) then air pressure might add to the "only goes one direction" effect.
sneak 5y ago
> Follower materials are highly patented, which means brands have protected their mixtures with patent protection. Highly patented!
kortex 5y ago
That was interesting but > These thickeners can range from particulate silica, alumina, titanium dioxide, or even powdered clay. If it were any of those, I imagine the stopper would be hazy, unless the refractive index of the matrix were very close to the aggregate. Curiosity abounds, the mind boggles. Might be a silicone (polydimethylsiloxane) based grease, with various silicone oxides and/or polymers as thickeners. Now I wanna take one apart.
- bayindirh 5y ago
  Pentel's Energel refills have two followers: first a transparent then a solid white one. Pilot's G1/G2 refills' stoppers are grease yellow / translucent orange. Similarly Faber Castell's Super True Gel refills are stopped by a composite follower. A transparent one, then a white one. Parker's gel refills' follower sometimes leaks and it is messy.
DrAwdeOccarim 5y ago
Looks like the patents outline it pretty well for the Pilot series: Polybutene 3SH, LUCANT HC-150, Fatty acid amide. Also a mention of mineral oil.

144 points by thomas 5y ago

EricE 5y ago

Nothing beats a Fisher Space Pen!

GloriousKoji 5y ago
I can attest to that. When I was a boy my parents gifted me a Cap-O-Matic space pen. It's a fairly generic looking pen with a small space shuttle logo in the middle of it but uses their patented pressurized ink cartridges. Of course like any boy I took it to school to show it off and use it until someone tried to steal it. It was super precious to me at the time so I stored it away in my precious items tin lunch box under my bed. It stat there for a couple of decades, forgotten through time. Like any well prepared person I keep a pen in the glove box of my car. The problem is they last only a couple of years before they leak or dry out which means they never work when I actually need them. One day I'm back home with my parents and I find my old tin and the Fisher space pen in it. It still worked perfectly and I figured if it's suppose to handle the rigors of space then a car glove box shouldn't be a problem. It wasn't. After about a decade in the glovebox of my old car it found its way to the glove box of my new car (which I guess is kinda old when compared to a car from today). It still works perfectly.
- mc32 5y ago
  That's a pretty awesome story to share. I may have to go find the one I was given many years ago too.
- Johnny555 5y ago
  The problem is they last only a couple of years before they leak or dry out which means they never work when I actually need them Of course, the other solution to this problem is just as in the apocryphal story [1] about the origins of the space pen... use a pencil instead. I keep a couple pencils and a $2 sharpener in the car. Of course, there are some situations where a pencil is not ideal (like writing a check), but if you really need to write something, it's always going to work. [1] https://www.scientificamerican.com/article/fact-or-fiction-nasa-spen/ https://www.scientificamerican.com/article/fact-or-fiction-n... https://www.snopes.com/fact-check/the-write-stuff/ https://www.snopes.com/fact-check/the-write-stuff/
  - taneq 5y ago
    Yeah, but... space pen!
  - gumby 5y ago
    I just use my pocket knife to sharpen pencils, but I live where it is legal to carry one.
    - eru 5y ago
      Aren't pocket knifes legal in most places? (I assume you mean some swiss army style folding knife?) Most because that kind of folding knife that doesn't lock in place would be less useful in a fight than leaving the knife folded and wrapping your hand around it as a weight.
    - irrational 5y ago
      Other than a place like an airplane, where is it illegal to carry a pocket knife?
      - ehvatum 5y ago
        UK, I imagine.
        agurk 5y ago
        Penknives are allowed to be carried without needing a justification in the UK. > It’s illegal to [...] carry a knife in public without good reason, unless it has a folding blade with a cutting edge 3 inches long or less [0] It also cannot be locking to not need a good reason to carry it. This is set in case law not the text of the relevant laws (and could could also probably be overturned if anyone had the time, money and inclination to challenge it). [0] https://www.gov.uk/buying-carrying-knives https://www.gov.uk/buying-carrying-knives
        deleted 5y ago
        [deleted]
- mike_d 5y ago
  > The problem is they last only a couple of years before they leak or dry out Are you not following proper protocol of swapping out for new pens between space missions?
powersurge360 5y ago
You (and others) might be pleased to know that you can get the space pen as a Parker refill that fits many different pen bodies. You can also get the very popular uni jet stream ink in the same refill type. I suggest a Kaweco sport as the pen body of choice
- c22 5y ago
  Thanks for this tip. I used to carry a space pen regularly but its small size and shape would slip out of my pockets and I would routinely find myself having to replace them.

bernulli 5y ago

“Gel ink is viscous, but it’s not thick enough to prevent it from flowing. This means it can evaporate over time” These are three different, unrelated phenomena. In a Newtonian fluid, no matter how large the viscosity, the fluid will flow when a shear stress is applied (think honey). A gel is instead typically a non-Newtonian fluid, i.e. a certain threshold stress has to be reached before motion sets in (think toothpaste). I don’t really see why the author then relates evaporation to viscosity. Shielding the fluid of interest from mixing with the surroundings will prevent evaporation (close the bottle of water and it will remain full, leave it open and then it will evaporate eventually).

andreareina 5y ago
> (think honey) or even pitch: https://en.wikipedia.org/wiki/Pitch_drop_experiment https://en.wikipedia.org/wiki/Pitch_drop_experiment
- bernulli 5y ago
  My favorite least exciting experiment!
aqme28 5y ago
> Shielding the fluid of interest from mixing with the surroundings will prevent evaporation (close the bottle of water and it will remain full, leave it open and then it will evaporate eventually). If you close the other end, pressure will prevent the ink from flowing out the tip.
- bernulli 5y ago
  Maybe, if it’s not about a bottle of water where we don’t want anything to flow out, one could use some sort of Transparent Material At The End Of A Gel Pen Refill to close the plastic pipe and prevent exposure to air to prevent evaporation!
- zaarn 5y ago
  There is gas pressure pens that have a small amount of pressurize inert gas at the end instead, which means that those are in fact closed on the end and operate much longer due to no evaporation issues.

throw_away 5y ago

Oh wow. Did not know that there was an ISO standard for pen refills: https://unsharpen.com/pen-refill-guide/ https://unsharpen.com/pen-refill-guide/

gumby 5y ago
But not fountain pen cartridges (the “international format” seems not to be an ISO standard). However there are ISO standards for the inks themselves, which can be the contents of these cartridges. Unsurprisingly there are also national ink standards. For example certain contracts like marriage licenses in Germany are only legal if signed with one of two DIN standard inks that are certified to last at least a century.
- mschuster91 5y ago
  > For example certain contracts like marriage licenses in Germany are only legal if signed with one of two DIN standard inks that are certified to last at least a century. German here. WTF? (Not that I don't believe it, but I couldn't find sources for that one)
  - richlogan 5y ago
    This is Iron Gall Ink I think - we have registrar ink here in the UK too. https://en.wikipedia.org/wiki/Iron_gall_ink https://en.wikipedia.org/wiki/Iron_gall_ink
    - wl 5y ago
      Iron gall ink is a poor choice for documents that should last a long time. It's an acidic ink, which damages paper. The iron rusts over time. The ink blooms. These things are manageable if the documents in question are stored in a cool, dry place. But why bother when there are better inks today?
  - mhd 5y ago
    I don't know about any special rules for marriage licenses, but for inks there's DIN/ISO 12757-2. Search for "Dokumentenechtheit". It's not that exotic, though. It gets a bit weird for printers. Laser and dot-matrix printers generally are okay, but you need a certified ink jet. Problem is that by the time they're certified, they might not be available. And then you only get the certification on proper paper, with the default inks, so don't cheap out on your old HP... As this is a ISO norm, too, I don't think this is something peculiar to Germany, after all, document storage isn't just a teutonic issue.

tryonenow 5y ago

They didn't really indicate why the end is sealed with a fluid as opposed to something physical. I suspect it's because flowing ink with a solid stopper would create a vacuum and quickly cease to function. A stopper is fluid and so can flow along with the ink. The space between the stopper and the shell is probably vented.

computator 5y ago
Yes, it's such an obvious question that's not addressed in the article. I was thinking about why they don't pinch the plastic tube closed at the point where the ink stops being filled. The following statement in one of the patents[1] seems to confirm your explanation: The aims of the arts are to make the ink follower follow the ink smoothly. [1] https://patents.google.com/patent/EP1002663A1/en https://patents.google.com/patent/EP1002663A1/en
ExtraE 5y ago
Not vented so much as just not air tight-- no reason to make it air tight, and the inside of the pen is by no means sealed, as you can tell if you've ever taken one apart (or had it explode inside your bag). The parts just don't fit that well together. Which I guess is a vent in a sense, although that's probably not the main design consideration. The (obvious) exception being the space pens, which do have some pressure chambers. They solve the vacuum issue by being pressurized, which has the nice benefit of letting them write upside down. I imagine they've made it viscous/non-Newtonian/whatever (not sure on the technical fluid mechanics term) enough such that gravity pushes/pulls it down towards the tip but prevents it from flowing the other way. Edit 1 (just before getting in the shower): Removed references to air pressure, as I don't think that makes a difference. Edit 2 (post shower): Air pressure might a difference after all, it depends on where the seal is. If there's an air tight seal on the tip end (which there might be, if that's how it's kept from leaking) then air pressure might add to the "only goes one direction" effect.

sneak 5y ago

> Follower materials are highly patented, which means brands have protected their mixtures with patent protection. Highly patented!

kortex 5y ago

That was interesting but > These thickeners can range from particulate silica, alumina, titanium dioxide, or even powdered clay. If it were any of those, I imagine the stopper would be hazy, unless the refractive index of the matrix were very close to the aggregate. Curiosity abounds, the mind boggles. Might be a silicone (polydimethylsiloxane) based grease, with various silicone oxides and/or polymers as thickeners. Now I wanna take one apart.

bayindirh 5y ago
Pentel's Energel refills have two followers: first a transparent then a solid white one. Pilot's G1/G2 refills' stoppers are grease yellow / translucent orange. Similarly Faber Castell's Super True Gel refills are stopped by a composite follower. A transparent one, then a white one. Parker's gel refills' follower sometimes leaks and it is messy.

DrAwdeOccarim 5y ago

Looks like the patents outline it pretty well for the Pilot series: Polybutene 3SH, LUCANT HC-150, Fatty acid amide. Also a mention of mineral oil.