Good morning everyone,
I came across this interesting forum while looking for 0.5 mm micro leads that could produce an indelible mark, allowing me to use my mechanical pencil instead of a pen.
My first question is: has anyone ever produced such leads?
If not, I’ve done some research and I believe it could be feasible. However, I work in the IT field, and developing this product would require expertise in engineering, materials science, and chemistry.
Is anyone interested in this topic?
I was messaging another member about this exact desire of mine yesterday.
My hope is to find the most pen like lead I can, in feel and performance.
They don’t make such lead as far as I know but i think it comes down to the leads b rating and finding that sweet spot. 2b, 3b, 4b and so forth.
The darker the lead, the softer it is so there’s got to be a magic zone for each lead size.
I’m personally starting my search as a 4b for 0.5, 3b for 0.4 and maybe a 5b or 6b (if possible) for 0.7 and 0.9.
I think as far as today’s technology is concerned, this is our best hope. Either that or retrofit a pen refill into a pencil (many do that as well)
Also, WELCOME, read and stay a while
I haven’t tried but would the waxier “for film” pencil leads they were developed to write on Mylar sheets, leave an indelible mark on conventional paper?
(At work already or I’d test it out)
BTW welcome to the forum @sdellava
This makes me think back to Parker’s Liquid Lead pens… an ‘ink’ cartridge that laid down a fluid graphite line. Product didn’t win over the masses… probably because it was more complicated than existing alternatives.
There may be a contradiction here: it’s the ink being liquid that allows pigments/dyes to reach deep in the paper, making it impossible to erase, while the deposit from a pencil remains on the surface of the page. However, in terms of durability, light resistance, etc. graphite tends to be better than most inks… as long as you don’t erase it.
Maybe as suggested by @Pdunc67 some waxy/greasy compound could combine the properties of the two but I wouldn’t bet much on it (especially if you’re looking for something that is legally recognised as indelebile, e.g. to sign documents).
There’s a few similarproducts, historically, to the idea you describe. I think some were produced as lead refills too- one that springs to mind is the Eberhard Faber ‘noblot ink pencil’ - example of the woodclinched here- Eberhard Faber Lot of 12 noblot ink pencils 705 with gold caps in original box. | eBay UK
In general, I find that thin and coloured lead cores tend to be much harder to erase.
There used to be copying pencils and copying lead cores — in 2.00mm, at least, and also in 1.18mm — which could and should achieve the desired results. Here in Italy, copying lead pencils are still used today when voting in any sort of official election, and they are chosen precisely because it is not possible to erase the mark once produced on the writing surface.
I’ll try with some “for film” lead (from Staedtler, or from Pentel): those ought to perform the frick as well.
Thanks for all usefull reply. I’ll look for some “for film” leads but I was looking for something different.
one idea is a coaxial lead made of “ink-solid” core + structural sheath
Here, the lead wears down through controlled abrasion: the core releases a thin “wet” film, while the sheath provides strength.
Sheath (20–60 µm):
Core (oleogel, “ink-pastel” type):
Pros: strong even at 0.5 mm; bold line, water-resistant (solvent version); scalable production via co-extrusion; no cavities requiring sealing.
Cons: feels more like an “ink pastel” than a water-based gel pen; glossy line on smooth papers (some love it, others less so).
or in alternative, Iron-composite lead “activated rust”
Concept: use very fine iron powder in a solid lubricated matrix. Friction releases Fe⁰ which, thanks to porosity plus mild saline–acid traces, immediately oxidizes to Fe₂O₃/FeOOH (dark brown).
Composition (indicative, % by weight):
Pros: natural color (brown/rust black), low-cost and safe ingredients (EN71-3 friendly), process similar to a traditional pencil lead (cold extrusion and curing).
Cons: on very smooth papers oxidation may be slower and “warmer” (brown) rather than black; ferric residues on fingers if the matrix is too fragile (can be tuned with wax/binder).
Other metals such as Manganese can also be used.
It seem strange to me that the big firms in the sector never tried this options
BTW - I sign a lot of documents at work in pencil - but the origs are always scanned and the paper is shreded.
You know those ‘perpetual pens’ with the metal tip? Damn hard to erase. But also not nice to draw with. The tips always feel draggy on paper unlike real graphite.
I find that thin and coloured lead cores tend to be much harder to eras
Mitsubishi developed thin, coloured leads to be erasable, in 2016:
ユニ ナノダイヤ カラー Uni Diamond Color
I have never tried them out though
That’s the idea, but with a more complex material structure
Indelible Lead Pencils have been produced since the 19th century, but I am unsure if they are actually indelible as advertised or not. Also, tax accountants asked for such pencils long ago in the 1920s. Sheaffer’s produced indelible leads in green color (I may have some of those). I think @Pdunc67 is correct about film leads, I will have ot try them when I get back home.
(Fineline Thick Indelible R25 Mechanical Pencil Leads 12 Boxes of 25 ~ 300 Total | #4751845534)
Also, are you familiar with the “Mark Sensing Leads” invented by IBM in the 1930s? They are erasable, but may work on film, and are also very dark (probably equivalent to 6B nowadays). Best leads I have ever used. They were only produced in 1.18mm (by IBM, Dur-O-Light, and Autopoint) or 1.9mm (by Waterbury).
Could you share a link to that?
Link to what?
Any photo or image.
Ok ok I’ve seen them, mark sensing leads, IBM packaging
Aha!
Here is a listing that I published with a super high price so it doesn’t sell 
But you can read the info in the listing about these leads. All are same grade of leads.
The 1.9mm are the rarest of all…
(Vintage Lot Assorted Mark Sense Leads: IBM, AUTOPOINT, DUR-O-LITE, and WATERBURY | eBay)
Got some those gathering dust ( so to speak)…
From which brand?
