Debate: a more systematically defined FLEX nib classification (based on large vintage 14k flex nib samples and data)

[duckbillclinton]

The current definition of flex nibs has many different proposals and suggestions online... 

 

FYI, I am not a collector... but for studying, and analyzing the science behind both vintage and modern flex nib designs, it is indeed my hobby.  With such in mind, to date, I have collected about 60+ vintage flex nib pens (all are 14K nibs, except a few very old Japanese Pilot steel flex nibs).  Due to my limited budget, a lot of these pens are not functional (missing ink sacs, missing levers, missing vacuum seals, and etc.), but all pen nibs are in working condition so their flex capabilities can be properly tested.  After trying out all 60+ vintage pens, I was able to rate and categorize them.  Among these pens, 4 pens have near no flex, 5 pens are semi flex (both these were bought carelessly), 25ish are full flex, 20ish are super flex, and 9 are wet noodles. 

 

With my collected data, I went online to find comparisons and references.  To my surprise and not so surprise, my findings are actually in sync with data from 2 very well organized and well presented online vintage pen shops...  (BV Pens, and Willow Strong Pens.  Please note that: I am NOT affiliated with any of them.)

 

At this point, I am confident that my findings are correct, so I came up with a slightly different and tuned proposal for categorizing pen nib flexibility.  We need to rate a nib not just by test writings (wet test), but we need to measure its performance with dry test also, and it should be done prior to wet test.

 

(To be continued soon)

 

 

[A Smug Dill]

Hmmm. Are you suggesting that a Platinum #3776 14K gold ‘Hard, firm’ UEF nib, or Platinum President 18K gold ’Hard, firm’ UEF nib, would put down a 0.6mm-wide line (let's say, over a line length of ≥3cm), due to its inherent ‘flex’ and therefore not be inelastically deformed or ‘sprung’ as a result?

[JulieParadise]

Where is @Bo Bo Olson when you need him? 😉 

[Aether]

OP is equating tine opening width with flexibility, and this is not always the case with vintage flex pens.   There are, for example, Waterman pink nibs that are exceptionally flexible but don't spread the tines wide. 

 

[DvdRiet]

  On 6/14/2022 at 8:29 AM, JulieParadise said:

Where is @Bo Bo Olson when you need him? 😉 

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I was just thinking the same thing!!

[dipper]

  On 6/14/2022 at 7:38 AM, duckbillclinton said:

we need to measure its performance with dry test also, and it should be done prior to wet test.

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That is a rational approach. It is looking at the tip of a very big iceberg though!

 

Viewed simply as a strange type of springy-widget-thing, a nib can be described by three categories of information:

 

• Its linear dimensions (as in an engineering drawing)
• How far it bends in various directions as a ratio to forces applied in various directions (the technical term is "compliance")
• How far it can bend in various directions and then return to it original form when the bending forces are removed ("elasticity").

 

Tabulating some of those factors, and splitting each factor into named categories, could be of use in sharing nib descriptions in an abreviated form without needing to list a long list of parameters. For example: "I got this pen today. Using the FPN nib categories terminology, it has a size 6 nib, German standard "F" tipping, tine compliance is "medium-high" in the vertical plane with tine-lift to tine-tip-separation ratio of 2.14. I have tested its elasticity to "SemiFlex" tine spacing - but don't want to risk pushing it any further than that."

 

The table posted by @duckbillclinton describes some aspects of two of the three categories I have listed above.

The upper rows define ten named categories of one linear dimension, "tipping width".

The lower rows define five named categories of elasticity as one parameter only, the width of tine gap opening that can be made without permanently deforming the tines.

The 10x5 block of cells at the bottom right calculate a little addition sum = tipping width + maximum tip separation, for each of the fifty possible combinations of categories.

 

In my opinion ......

 

The named categories are reasonable proposals to lay on the table for debate. Many alternative categories could be proposed of course.

 

One problem with the flex name categories is that those names are already in common use, with different meanings adopted by different users. It may be better to create new names that have no history of previous meanings.

 

The math in the 10x5 block of cells is valid as an exercise in addition. Note though that the summed values use the maximum values of each range of tine opening categories. The relevance of those summed values is debatable. Summing may imply a prediction of line widths. The original proposal mentioned defining nibs in the "dry" state. That makes sense to me. When inked and laying down a line on paper things become much more complicated than the nib "dry" description. An overall tipping blob width of 0.4mm, flexed to a tine separation of 0.3mm, is indeed a physical object of 0.4mm + 0.3mm = 0.7mm overall width. Inky line width might be anything from 0.3mm to 0.7mm or over 0.7mm with some nib/pen/ink/paper combinations.

 

The table of "dry" categories can be expanded in many ways.

Each of my three groupings of dry nib descriptions ("linear dimensions", "compliances", and "elasticities") are multi-faceted properties.

The categories originally tabled for debate describe just one facet of a nibs linear dimensions, and just one facet of elasticity. Other commentors have already mentioned further facets that are important, such as how far tine tips flex upwards before reaching their elastic-limit (yield point). And compliance (movement vs force applied) has not yet been mentioned in this topic.

 

There is plenty of opportunity to explore more of this enormous iceberg. How far that quest is worth pursuing is a matter of choice. Choice depends on what you wish to achieve.

[Geert Jan]

I think I'm missing information on the force applied to achieve the flex. Not saying thta all nibs will flex as long as you apply enough pressure; non-flex nibs will just deform. What's the point of knowing how much a nib can flex if you don't know how much pressure is needed. As an example: I have an FPN flex nib thta requires too much effort (for me) to achieve even a minimal amount of flex, adn an FPNibs flex where I have to put in a significant effort not to flex it...
Don't know if I quite agree with the general American/European/Japanese nib widths either; that's far more specific to individual manufacturers (even if Japanese nibs are generally a bit narrower)

[txomsy]

Yep, where is @Bo Bo Olson?

 

Anyway, the table is inherently flawed. If I use a 1.5 mm stub, then, does it mean that it is "Flex"? How much line variation is obtained is not substantial.

 

And what if I use an XXF nib that can go to 1mm? or a broad that can go from 1 to 1.6mm? Again it is not line variation that matters.

 

It is more important how much relative variation can be obtained. A nib that goes from 0.1mm to 1mm has a 10x line variation, while one that goes from 0.5 to 2.1mm only has 4x. Yet one has opened < 1mm and the other >1.5mm.

 

Then, any nib can give any variation given you apply enough force (even if you need a pair of tweezers). Yeah, it will be sprung but will give you that variation.

 

Which comes to the other point: plasticity vs. flexibility (defined as elasticity). If you deform the nib, it is not flexible, it is plastic. If it returns quickly to its original position (it is springy) then it is flexible, not plastic. And in between you have nibs that return quicker than others, so they would be more or less elastic.

 

In defining how "flex" a nib is, one needs to consider, of course how much do tines spread, but relative to the relaxed status, i.e. relative line width change, and then, how much force is required to obtain that variation, and then again, whether the nib recovers afterwards or not, and how much and how fast does it recover.

 

A more useful classification would be to define a "gold standard" that can be easily referred to (say, a Zebra-G nib) and then compare with it.

 

That or an "absolute" scale based on "relative" line variation (times un-pressed width), which can be measured with a loupe or microscope, amount of pressure needed to achieve some times line variation (e.g. 2x) which can be measured using a balance coupled to a loupe or microscope, and elastic recovery (which can be measured with a precision chronometer coupled to a precision balance coupled to a loupe or microscope.

 

And then, even so, I am certain that there are additional properties I am ignoring and should also be taken into account.

 

Edit: fatigue of materials, for example: some materials/designs may show flexibility but only for a given time before they break, become rigid or deform definitively, so lasting flexibility should be a factor too. One does not want a nib that works for one month and then breaks. Or rust resistance, the reason we do not use dip nibs in fountain pens despite their wonderful flex properties. And surely many others will come up.

 

As a starting point, absolute width variation is a poor standard, specially with the variability of nibs available.

[duckbillclinton]

  On 6/14/2022 at 2:23 PM, dipper said:

That is a rational approach. It is looking at the tip of a very big iceberg though!

 

Viewed simply as a strange type of springy-widget-thing, a nib can be described by three categories of information:

 

• Its linear dimensions (as in an engineering drawing)
• How far it bends in various directions as a ratio to forces applied in various directions (the technical term is "compliance")
• How far it can bend in various directions and then return to it original form when the bending forces are removed ("elasticity").

 

Tabulating some of those factors, and splitting each factor into named categories, could be of use in sharing nib descriptions in an abreviated form without needing to list a long list of parameters. For example: "I got this pen today. Using the FPN nib categories terminology, it has a size 6 nib, German standard "F" tipping, tine compliance is "medium-high" in the vertical plane with tine-lift to tine-tip-separation ratio of 2.14. I have tested its elasticity to "SemiFlex" tine spacing - but don't want to risk pushing it any further than that."

 

The table posted by @duckbillclinton describes some aspects of two of the three categories I have listed above.

The upper rows define ten named categories of one linear dimension, "tipping width".

The lower rows define five named categories of elasticity as one parameter only, the width of tine gap opening that can be made without permanently deforming the tines.

The 10x5 block of cells at the bottom right calculate a little addition sum = tipping width + maximum tip separation, for each of the fifty possible combinations of categories.

 

In my opinion ......

 

The named categories are reasonable proposals to lay on the table for debate. Many alternative categories could be proposed of course.

 

One problem with the flex name categories is that those names are already in common use, with different meanings adopted by different users. It may be better to create new names that have no history of previous meanings.

 

The math in the 10x5 block of cells is valid as an exercise in addition. Note though that the summed values use the maximum values of each range of tine opening categories. The relevance of those summed values is debatable. Summing may imply a prediction of line widths. The original proposal mentioned defining nibs in the "dry" state. That makes sense to me. When inked and laying down a line on paper things become much more complicated than the nib "dry" description. An overall tipping blob width of 0.4mm, flexed to a tine separation of 0.3mm, is indeed a physical object of 0.4mm + 0.3mm = 0.7mm overall width. Inky line width might be anything from 0.3mm to 0.7mm or over 0.7mm with some nib/pen/ink/paper combinations.

 

The table of "dry" categories can be expanded in many ways.

Each of my three groupings of dry nib descriptions ("linear dimensions", "compliances", and "elasticities") are multi-faceted properties.

The categories originally tabled for debate describe just one facet of a nibs linear dimensions, and just one facet of elasticity. Other commentors have already mentioned further facets that are important, such as how far tine tips flex upwards before reaching their elastic-limit (yield point). And compliance (movement vs force applied) has not yet been mentioned in this topic.

 

There is plenty of opportunity to explore more of this enormous iceberg. How far that quest is worth pursuing is a matter of choice. Choice depends on what you wish to achieve.

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Very well said.  I will continue my post later this week, and hopefully most of the readers will eventually get what I am trying to propose.

 

Oh, by the way, @dipper please checkout my posts on the Experiment with Flex thread also.

[dipper]

  On 6/14/2022 at 4:39 PM, duckbillclinton said:

Oh, by the way, @dipper please checkout my posts on the Experiment with Flex thread also.

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I am a long-time avid fan of that thread. 🤓🤓🤓🤓🤓🤓

[Aether]

  Quote

We need to rate a nib not just by test writings (wet test), but we need to measure its performance with dry test also, and it should be done prior to wet test.

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The flexibility of a nib is not correlated with whether it has ink on it or not.  So what kind of performance are you expecting to measure with a 'dry' nib? 

 

Today there is an obsession with quantifying everything, but when it comes to nibs it doesn't matter what scale or measure you use it will never inform how a nib feels to use.  A large part of this equation relates to the hand of the user, and this is a critical factor that does not appear in your table. 

[A Smug Dill]

  On 6/15/2022 at 3:45 AM, Aether said:

Today there is an obsession with quantifying everything,

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I see no problem with that. I have a problem with consumers and interested parties expecting that the information would be made available by someone else — manufacturers, retailers, semi-pro or amateur reviewers among fellow hobbyists — at the latter's expense and effort, while the former just sit back waiting to be serviced, and given the benefit of a database covering all the available options so that they can be ‘smart’ and spend their own money only on the ‘best’ suited models out of the lot.

 

No, whoever wants that database of quantified information about various pens should build it at his/her/their cost; and then they can choose whether to share — freely or otherwise — that inevitably limited subset they have on hand, since realistically nobody can stay on top and keep abreast of what is current and new and test them all.

 

If this thread is just about developing yet another scale for quantification to suit one's purpose, that the industry is not going to adopt as a common standard, I think it's perfectly fine as an intellectual exercise.

[txomsy]

So, what about Wikipedia? Android? Apps? Public libraries?

 

Despite all we may individually want to believe, it seems that at some points in time, in some societies and cultural backgrounds, cooperation and free sharing of knowledge is a strong drive. So much so that it tends to overcome non-shared products and become standard in specific markets, even in spite of the efforts of strong corporate players to subvert that cooperation.

 

I think that there may be and ecosystem of people willing to freely contribute to building up a body of knowledge (on pens, on nibs, on brands, on and on...) and share it for free. It would be then simplistic to say someone should do it at their own cost, for likely very few would invest all the cost of building a comprehensive database, but a great many may be willing to give their 2c. worth to fund a tiny part with the sum being much, much larger than what any motivated individual (no matter how wealthy) would be able to do. After all, that is one of the largest added values of the FPN itself.

 

Planets didn't come up from a huge rock but by accretion of planetesimals. So, what about the Earth?

 

It is then each one's privilege to opt in or out. But I see no reason why it need not be done or someone may not propose to get the ball rolling. We are not mice after all, and this is not like hanging a bell on a cat's necklace. It may start as a divertimento and end up being a serious resource.

 

DISCLAIMER: I directed a publicly funded intercontinental project to promote use and development of free, libre and open source software ten years ago. My views may be strongly biased by the successful business cases and strategies we touted. Even so, I think there are many ways to skin a cat and get a job done. Far from me to tell anyone what they should do, though I believe in sharing information to make better educated strategic decisions.

[InesF]

  On 6/15/2022 at 7:11 AM, txomsy said:

It is then each one's privilege to opt in or out. But I see no reason why it need not be done or someone may not propose to get the ball rolling. We are not mice after all, and this is not like hanging a bell on a cat's necklace. It may start as a divertimento and end up being a serious resource.

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What you give away for free will be yours forever,

what you keep for yourself is lost for the world.

-- Eric Emmanuel Schmidt

 

The attempt of trying to make a more objectively based classification of flex is to honour.

The subjective impression of writing with a flex nib is to honour as well - and needs to be integrated.

 

A comprehensive and reliable classification will be, most probably, way more complex than what I have read in this (and in the other, subjectively coloured) thread so far.

[A Smug Dill]

  On 6/15/2022 at 7:11 AM, txomsy said:

So, what about Wikipedia? Android? Apps? Public libraries?

 

Despite all we may individually want to believe, it seems that at some points in time, in some societies and cultural backgrounds, cooperation and free sharing of knowledge is a strong drive.

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I'm not sure whether or not that was a reply primarily addressed to me, or at least addressing what I wrote earlier in this thread.

 

I'm not against Wikipedia and such. I use Wikipedia a lot, and I'm grateful for its existence and its contributors. But, as I said, I have a problem with consumers and interested parties expecting those things to exist (or be built) and improved upon on someone else's dime, just so they themselves can benefit. If a would-be beneficiary:

• isn't personally spending the money and effort to develop and realise what he/she wants to see available to the likes of him/her;
• isn't somehow important enough through human relationships and community/social politics to influence those with the capability (and/or discretionary ‘spare’ capacity) to make it happen, without something transactional or commercial being in play; and
• doesn't and can't know that those parties with the capability are otherwise bound by law, enforceable undertakings, vows, pledges, obligations due some sort of debt, geasa, or doctrines to which they voluntarily subscribe, to build and deliver such things “for the common good”,

then in my opinion it would be unreasonable for him/her to have an expectation that such public access to the desired information resources will come to exist and continue to exist.

 

It's one thing to propose a scale for expressing temperatures; Fahrenheit, Celsius, and Kelvin temperature scales already exist, but one could always propose yet another, different one if he/she finds what is there is unsatisfactory for expressing what is to be measured. It's an entirely different thing to measure the boiling and melting points of different substances, compile it all into a database, and make it available to everyone to freely access because there would be some benefit; if that database doesn't already exist, then it's unreasonable for the would-be beneficiary to expect others to just go ahead and build it at their cost, when said beneficiary isn't offering to at least contribute more than the benefit he/she stands to receive from the existence of such a thing.

 

I'm more than happy to ‘debate’ the sort of scale, or method of quantification, that the O.P. wants to talk about in this thread. That's not the same as saying that I think 1. such a scale should exist, and 2. be adopted as a common standard to facilitate communication and general understanding between the community, and 3. someone then needs to get on with it to measure and share the flex measurements on this new scale for all the nibs that exist in the market, just so would-be buyers could then make better informed decisions.

[arcfide]

I seem to see more engineering style graphs of function from Platinum than most of the other makers. Funnily enough, they've recently released a graph on the flexibility of their new anniversary pen nib:

 

ディケイド特別ページ（英語版） (platinum-pen.co.jp)

 

Note in the above that they don't focus on line variation when they talk about softness, but instead, just the relative rate of deformation for a given pressure. At the very least, you at least get the idea of what Platinum considers "soft and flexible". 

[Bo Bo Olson]

Buy a regular flex pen...and then look up my system of halves.

It don't work with out a regular flex pen...Japanese call that 'soft'. I call it regular flex, in that was often the nib flex in the '50-60's on many pens that one bought.

 

Many folks don't care for my system but have nothing to replace it with.

I foolishly never did a link on that; just one to one; eye to eye...broken record...type it out 'live' every time....talking to someone.

 

Folks tried to do superflex with electronic scales ....that was very ill liked.

 

My system of halves is horseshoe or hand grenade close. Nothing you can measure with an instrument....that has been tried and jumped on by those who understand instruments.

 

I find semi&maxi to clump together.

I find my system works...all the way out to the Weak Kneed Wet Noodle ..an pre-23 MB safety Pen.....

There it skips an expected place in my system...........but what a nib.

 

Weak Kneed Wet Noodle was named by John Swobada (sp), the English nib grinder. I never expected to own one.................and sadly in spite of my many promises.....still haven't tried to learn to write.

 

If you are sueprflex noobie my system works, but once you have 5-10 of them they merge or overlap. Marcio(sp) (use to have his name taped on my desk.)

He sells superflex nibed pens.........and don't care for my system in superflex. I know he's right, but for noobies....I think my system tells yep.....you got two elbows.

 

I do have two 52's from him. One a two stage 7X Wet Noodle the other a 6X Wet Noodle. My best Wet Noodle is a Soennecken nib that goes 7x.

Wet Noodle has more to do with ease of tine spread than width....IMO.

 

Actually 7 X is rare outside of someone springing his nib on Youtube or selling you a probably sprung nib on Ebay with a paper trail of a nib that is well over extended.

 

Do read Marcio(sp)'s blog.........it is golden.

 

[Aether]

Waterman had:

 

Purple, Accountant.

Pink, Bookkeeper.

Black, Stenographer.

Brown, Fine Flex.

Green, Med. Firm.

Red, Med. Flex.

Blue, Stub.

White, Coarse.

Yellow, Left Handed.

 

That was good enough for back in the day, it's good enough now.  Our current obsession with splitting hairs - take note post above this one -does not add anything but unnecessary confusion.

[duckbillclinton]

  On 6/14/2022 at 2:23 PM, dipper said:

That is a rational approach. It is looking at the tip of a very big iceberg though!

 

Viewed simply as a strange type of springy-widget-thing, a nib can be described by three categories of information:

 

• Its linear dimensions (as in an engineering drawing)
• How far it bends in various directions as a ratio to forces applied in various directions (the technical term is "compliance")
• How far it can bend in various directions and then return to it original form when the bending forces are removed ("elasticity").

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(continue from previous post)

 

@dipper Your reply is equally rational and professional (I am guessing you might be an engineer or a scholar in related fields).  👍👍👍 

 

Your analysis is precise, my so called vintage "Vintage Nib Flexibility Comparison (14K Gold Nib, Dry Test)" table is indeed just a overly simplified way of describing how a flex nib should behave like...  However, there was a mistake in the table, the tine opening should have been a 0.4mm step, instead of 0.5mm.  Japanese tip size UEF has also been removed as I have yet to find a 0.1mm tipped flex nib online (or, from any of my friends' possessions).  Here's the revised table,

 

 

The above table did not come from no where, it is based on actual statistics from a large population of vintage 14K gold flex nib pens' test data, and it is a proper statistical summary of a very complicated problem.  While many readers quickly raise doubts and criticize this table... maybe... they should pay more attention to the details, and please, check out BV pens and Willy Strong Pens websites, there are at least a few hundred different brand and model vintage 14K gold flex nib pens (sold or in stock) with legit tests, including sample write and caliper measurement photos.  Their presentation is very accurate and well organized.  Please search each of the categories with keyword wet noodle/ super flex/ flex/ semi flex, and find out how wide each flex nib writes with caliper measurement.  You will then understand why they are in-sync with my proposal above (based on the now near 70ish vintage flex pens' data). 

 

To be honest, these 2 sites are the best if any forum members want to research more on vintage flex nibs, especially on how they write and flex, and I couldn't find any other sites that can even come close.  After all, we shall not forget the simple fact that fountain pens were invented for daily writings and frequent use, for extensive calligraphy and art works, dip nib pens will be a more viable solution instead.  With such in mind, all pen makers in the old days made nibs flexed within a certain range which is mostly suited for general purpose writings, regardless of materials, nib size/ thickness/ shape (geometry), and tip size.  BV Pens and Willy Strong Pens have mostly the vintage size 2 nibs tested, and they also have some size 1, 3, 4, and larger nib pens tested as well.  Their data is a proper representation of what vintage 14k flex nib pens would perform and what range of flex they would fall into.

 

On the other hand, I understand some of the readers raised questions about material.  Well... in the case of 14K and 18K...  The truth is, even within the 14K gold definition, there could be many variations in the chemical composition.  14K means the alloy contains at least 58.33% gold, the remainder is other alloying elements and impurities, this can take a very wide range of combinations, like professor @antoniosz pointed out from the other post, chemical composition will determine elastic modulus/ Young's modulus (stiffness), and will not be affected by heat treatment (or any other factors like cold work, nib shape, and etc.).  Elastic modulus corresponds to how easily a nib can be bended.  Cold work (rolling, pressing, stamping) will improve yield strength which represents how much a nib can resist deformation while flexing.  So, an ideal flex nib should have the combination of low elastic modulus and high yield strength, this will make the nib easy to bend and can flex more without deforming.  With such in mind, since we also have to consider corrosion resistance (corrosion by ink), naturally gold alloy become a very ideal material for making fountain pen nibs, 

 

Nibs made by different makers will have different chemical composition (as each has its own formula), nibs made by the same makers in different models may have different chemical composition for different looks (yellow gold, rose gold, white gold, and etc.)  So arguing the Ks of gold alloy, is really meaningless.

 

Add to the above, pure gold alone is not a good material for making fountain pen nibs.  Just FYI, in the 70s and 80s, the 3 major Japanese fountain pen makers had a gold nib war, each tried to raise the Ks as high as possible.  Pilot quickly withdrew as they valued more on nib performance, so they ended up with 22K nibs.  Platinum and Sailor both had 23K nibs for a while, but at the end Sailor won out by ultimately releasing the 24K gold nibs (it's actually 23.5K but according to jewelry standard it could be rounded up).  Besides the hard to find and expensive Sailor 24K nib pens, I personally own Pilot's 22K nib pens, and 23K pens from Platinum and Sailor, none of these are flex .  That's not a surprise because high gold content means the nib material will be soft by default, so they were cold rolled/ pressed to hard state to prevent deforming during use. 

 

Gold Alloy, on the other hand, is good for making fountain pen nibs, especially the lower K gold alloys, they are good for making flex nibs.  With added alloying elements like copper, nickel, and etc., gold alloy receive higher strength with small increase of elastic modulus.  After all, the properties that make Gold a good material for general use fountain pen nibs is its corrosion resistance, and Gold's low elastic modulus of 79 GPa makes gold alloy a good material for flex nibs.  Please keep in mind that we are using gold alloy to make nibs, but not pure gold. 

 

Previously on another thread, there was a debate on whether platinum is a suitable material for making flex nibs, why not?  First of all, platinum is NOT brittle, it's a stronger material than gold, and it's the most malleable metal next to gold.  See below table extracted from a science journal for pure gold and pure platinum's ultimate tensile strength both in anneal state and after cold work, material science data don't lie, platinum is stronger than gold.  Our perception sometimes can fool us.  However, this argument is completely irrelevant because no one will use pure platinum to make fountain pen nibs!

 

The original link for the above journal:  https://www.technology.matthey.com/article/57/3/202-213/#:~:text=The alloys covered are of,%2C ruthenium%2C gold and nickel.

 

Secondly, if we use platinum to make a flex nib, we will use lower number 14K, or 18K platinum alloys.  The property we want from platinum is its corrosion resistance.  A small drawback about platinum is its elastic modulus, which is at 168 GPa... a bit high... its alloy's elastic modulus is going to be around there.  However, 316 stainless steel has elastic modulus of 190 (minimum), and there are plenty of vintage stainless steel flex nib pens (made by Japanese and European makers), they perform just as well as gold nibs.  With such in mind, we are absolutely certain there will be some certain platinum alloy combinations will be suitable for making flex nibs, one of the wild guess might be 80-20 platinum nickel alloy listed in the above journal, it has good strength after cold work (well, the elastic modulus is unknown though).  The question about platinum alloy flex nibs though, is whether any pen makers are willing to test and find the right alloy, and make an actual pen.

 

 

@dipper In addition, your quick recognition of "Dry Test" is priceless.  An inked pen, WILL, have many new variables added to the already complicated case of flex nib classification.  To simplify our test, and to make it more accurate and fair, flex nib should be measured with at least 2 tests-- Dry Test, and Inked Test.  This will remove a lot of the undesired variables introduced by feed, ink, and paper.  Regarding the 3 categories of information, due to the lack of my free time, I will slowly address each with more details in my future posts. 

 

For the time being, regarding linear dimension, bigger nibs don't equal to wider tine openings.  Contradict to many believes, a lot of the size 4, 5, 6 vintage flex nib fountain pen's spread their tines just like size 2 and 3 nibs, they don't spread wider, and they are harder to spread as well.  A modern day example would be Pilot's FA nibs, for their model 743 (Pilot nib size 15) compare to model 742 (Pilot nib size 10), both open their tines with identical width, but 743 feels harder, and 742 is more pleasant to flex write (I own several of these, so I know😉).  I never had the money to afford a Waterman 7 Pink, but I do own one of the 30s InkVue with large keyhole nib (I guess it may perform like a 7 Red), the nib is much bigger than the 52s, but it opens just like 52s, identical width, and it feels harder as well.  Same goes to a size 4 Moore nib I bought, it's not much better than a Moore 92 but it's a lot harder to open.  Same applies to vintage Pilot flex pens as well, size 4 opens just like size 2...  Supposedly, larger nibs meaning the center slit is longer/ deeper, so tines can open more, but why they don't open more?  Well, that's because like mentioned above, pen makers will only make their flexible fountain pens to flex within a reasonable range for general purpose writings, so they either cold work the larger nibs to a harder state, or they reduce the curvature at the front of the nib, or they reduce the slit depth, to make these lager nibs to flex the same width with smaller nibs.  To be honest, I found size 2 and 3 vintage flex nibs are the most comfortable for flex writings.

 

Regarding compliance, the revised table by me from above should more or less match the 2 vintage flex pen shops mentioned.  It's more of a statistical summary than just a simple addition calculation.  Regarding elasticity though, without any lab equipment or a well defined/ well controlled set of rules, it's going to be tough to measure.  I very much agree with our very knowledgeable flex nib fan @Bo Bo Olson 's opinion on digital (electronic) scale.😊  With some tweaking on the testing steps, we should be able to measure elasticity with reasonable accuracy with a digital scale (indeed).  Here are my proposed steps,

 

1. Dry test a flex nib on a sticky label, write wide strokes/ marks as wide as possible without deforming the nib, measure the widest marks with caliper, record the data, and highlight these wide marks on the label

2. Peel off the label and stick it on top of the digital scale, turn on the scale and reset it to zero (so label's weight will be zeroed)

3. Without interfering the scale, flex bend/ write the nib to match the highlighted marks on label, record down the max scale readings.  This should give you (roughly) an idea of how many grams of force is required to flex your nib to it's max allowable width.

 

However, there are many shortcomings on the above proposal, for example, the contact angle between the nib and the writing surface is not considered, the force to start the flex bend is hard to read from the scale, the entire force curve (variable of force required at different point of flex bend) is also hard to sample...   Oh well...  At least, we have something to measure.

 

Besides the above, @dipper, like you mentioned, there are still way too many things we have yet to consider.  I will give one example, most of the people had never considered gravity will be an important factor for flex nib designs, especially the Brachistochrone curve, a cycloid equation related problem.  Why Brachistochrone curve is important, and is related?  Well...

 

1.  Ink flow during flex writing is sustained by the stabilized ink film created between the opened tines and paper, without this ink film, the pen will railroad. 

2. At the top of the tine opening, ink is supplied through either breath hole, top of the slit, or the nib body itself with contact from the feed by capillary action.  When ink supply reaches ink film, it "flows" underneath it.

3.  As soon as ink supply reaches ink film, gravity start to take over and play the tricks (as capillary action is no longer relevant in this scenario).  When gravity is part of the driving force for ink flow, according to physics laws, a straight slope surface is not going to be the fastest surface for ink to flow down.  Instead, just like rolling a ball down the hill, the slope with a curved surface will require the shortest time for the ball to reach to its target, more precisely, this curve is a Brachistochrone curve, a cycloid equation.

4.  When we force bend a stick from the two ends, its bending shape is a hyperbola.  This applies to the scenario when we flex bend a nib.

 

So what does the above mean?  It means softer flexible nibs like gold nibs, will have a better ink flow surface than harder stainless steel flexible nibs in the path of ink film created by tine opening.  Vintage gold flex nibs are soft, when they flex bend, besides the tines spread open, the tines also bend up with curve, not exactly a Brachistochrone curve, but this will change the somewhat flat sloped ink film to become a hyperbolic slope, so ink flows down faster, with more efficient ink supply, ink film is more stable and less likely to rupture, also the nib writes wetter.  When I modify regular modern stainless steel nibs to flex nibs, I start to realize the above.  Because stainless steel is a lot stiffer than 14K gold, no matter how much I thin down the nib, it will never be able to bend like gold alloy, the nib can be modified to allow tines open even wider than the vintage gold nibs, but ink flow underneath the ink film will never be as good as gold nibs, and the ink film is easy to rupture.

 

(to be continued)

 

 

[Aether]

Jeez. 

 

I don't doubt the measurements, but I do doubt the usefulness of them.  Until relatively recently pen users didn't need any kind of graduated scale or book of measurements regarding the precise properties of a given nib.  Actually they mostly still don't.