# Pens, markers and highlighters: research notes

Date: 2026-10-25. Scope: hand-held writing and marking instruments: ballpoint, hybrid, gel, liquid rollerball and fountain pens (including multi-pens), fineliners, colouring and art markers (children's washable fibre pens, water-based brush pens, alcohol illustration markers), markers for objects and boards (water-based, permanent, dry-erase, wet-erase, liquid chalk, paint) and highlighters (liquid, gel, dry). Not the refills, cartridges and leads themselves (sibling `ink-cartridges`), bottled ink (sibling `ink-cartridges`, and `paint` under crafts for art inks), pencils, crayons and pastels (sibling `pencils`), correction pens (sibling `correction-products`) or whiteboards (sibling `stationery-boards`). Overlaps are left to those siblings: this register keeps only the pen's side of them (which refill or cartridge it takes, which surface a marker writes on). Overlap rule added after the blind check: a product sold as a pen or marker stays in this leaf even when a sibling also lists it: paint markers (crafts `paint`, Paints, Inks & Dyes), brush, calligraphy and fabric markers (crafts `brush-stamp-tools`, Brushes, Stamps & Marking Tools), children's drawing sets (play `play-dough`, Play Dough, Putty & Drawing). Dry highlighter pencils stay here as `highlighter_format` dry while `pencils` has no highlighter medium. Consistent with siblings: `stationery-boards` hands dry-erase markers here and `ink-cartridges` hands pen-plus-refill bundles here.

Quote labels: **verbatim** = the sentence in quotation marks was in text I read myself (pdftotext on a downloaded PDF, or curl plus HTML stripping into the scratchpad, `/private/tmp/claude-501/-Users-amnbh-Desktop-dev-zamana/94e1e673-5231-41fe-8b68-7a624ab5c8d8/scratchpad/pens/`); **fetched excerpt** = a fetch tool summarised the page; **search excerpt** = the claim came only from a search-engine summary. No search-excerpt-only number is in category.json. Every quote below is verbatim unless labelled otherwise.

## Seed

Seed output (verbatim, abridged to the two headers and their content lines):

```
=== Example entry (from an unrelated category) ===
category: olive-oil
what this shows: a facet that experts rank first, that almost no listing carries, and that is expensive to backfill. The honest answer is to list it, mark it researched, and limit backfill to the top of the catalog. Also shows a derived metric hanging off a researched facet.
<example> { "id": "harvest_date", "label": "Harvest date", ... "source": "researched", "backfill_cost": "high", ... } </example>
Derived metric that follows from it: { "id": "months_since_harvest", "formula": "months_between(today, harvest_date)", ... }

=== Persona ===
A tailor, who thinks in fit, drape and what you can alter afterwards

Ask yourself two things and write the answers under 'Seed' in notes.md:
  1. What is the pens equivalent of the example above?
  2. What would this persona notice first about pens that a typical buyer would not?
Keep what survives the data check. Drop the rest.
```

1. **The pens equivalent of harvest date is documentary permanence.** Experts who sign contracts, keep records or write cheques care first whether the line survives water, light, bleach and erasure, and an ISO standard tests exactly that (ISO 12757-2 DOC for ballpoints, ISO 14145-2 for rollerballs). Almost no listing carries the DOC marking; brands say "archival" or "fraud-resistant" without naming a test. **Kept** as the `permanence` split, marked researched, with a judgement that brand words are not a test. The derived-metric half of the analogy was write-out length (metres per refill) feeding cost per metre. **Dropped**: no two fetched sources gave comparable write-out figures, and the search budget ran out before I could find a second.
2. **The tailor notices fit and what can be altered afterwards.** Fit survived as the line fitting the handwriting (`line_class`), with the expert correction that the printed size is the ball, not the line. Alteration survived as `refill_path`: whether a fountain pen takes standard international cartridges or only its maker's, whether a ball-pen refill fits across a range (it does not for uni 207 and 207 IMPACT), and whether a highlighter or marker refills from ink. **Dropped**: grip diameter, weight and balance. They are what a tailor would measure first, but no brand page I read publishes grip diameter, and the photo answers most of it.

## Sources and what each supports

### Standards bodies and regulators (the safety and permanence rules)

**ISO 11540:2021, Writing and marking instruments: Specification for caps to reduce the risk of asphyxiation (iTeh preview PDF, pdftotext)**
https://cdn.standards.iteh.ai/samples/81889/9c3d070a4cea43d5af38070f80582924/ISO-11540-2021.pdf
- verbatim: "This document specifies requirements to reduce the risk of asphyxiation from caps for writing and marking instruments. It relates to such instruments which in normal or foreseeable circumstances are likely to be used by children up to the age of 14 years."
- verbatim: not applicable to "writing and marking instruments which are designed or only intended for use by adults, e.g. jewellery pens, expensive fountain pens, professional technical pens".
- verbatim: "A way of avoiding the risk of inhalation of caps of writing and marking instruments is to manufacture products without caps whenever possible."
- verbatim: "Caps shall conform to at least one of the following: 4.2 or 4.3." 4.2: a cap introduced to a "16" mm "ring gauge" where "at least 5 mm of the length shall not enter under its own weight". 4.3: "caps shall permit a minimum air flow of 8 l/min, measured at room temperature, with a maximum pressure drop of 1,33 kPa."
- Supports: the cap judgement. Confidence high.

**ISO 11540:2014 preview** https://cdn.standards.iteh.ai/samples/56728/1242fdf4b4aa4dd089fc75d172f7a966/ISO-11540-2014.pdf
- verbatim: "caps shall permit a minimum air flow of 8 l/min, measured at room temperature, with a maximum pressure drop of 1,33 kPa"; "likely to be used by children up to the age of 14 years".
- Supports: second source for the 8 l/min and age-14 figures (same body, previous edition). The search summary for ISO 11540 also gave 8 l/min (search excerpt). The 8 l/min and 16 mm figures are kept in the ISO reference's `supports` line but not in a facet, since the pipeline cannot test a cap.

**ISO 12757-2:1998, Ball point pens and refills, Part 2: Documentary use (DOC) (SIS preview PDF, pdftotext)**
https://www.sis.se/api/document/preview/612121/
- verbatim: "pens which meet the requirements for documentary use produce lines which are more resistant to modification (e.g. attempts to falsify a document) than those for general use."
- verbatim requirement headings: "4.2 Erasure resistance", "4.3 Ethanol resistance", "4.4 Hydrochloric acid resistance", "4.5 Ammonium hydroxide resistance", "4.6 Bleaching resistance", "4.7 Water resistance", "4.8 Light resistance"; each "The line shall remain visible when tested as specified".
- Search excerpt (not used for a number): the designation example "Ball point pen ISO 12757-2 M DOC".
- Supports: what document grade means. Confidence high.

**16 CFR 1500.14(b)(8), via Cornell LII** https://www.law.cornell.edu/cfr/text/16/1500.14
- verbatim: LHAMA "provides that, as of November 18, 1990, 'the requirements for the labeling of art materials set forth in the version of the standard of the American Society for Testing and Materials ['ASTM'] designated D-4236 ... shall be deemed to be a regulation'".
- verbatim: "The producer or repackager of art materials shall submit art material product formulation(s) or reformulation(s) to a toxicologist for review".
- verbatim: not art materials: "Products whose intended general use is not to create art (e.g., common wood pencils, and single colored pens, markers, and chalk), unless the particular product is specifically packaged, promoted, or marketed in a manner that would lead a reasonable person to conclude that it is intended for use as an art material." and "packages of multiple colored pencils, chalks, or markers unless promoted for non-art materials uses are likely to be art materials".
- Supports: LHAMA scope, the single-colour exemption. Confidence high. The CPSC art-materials business guidance page returned a 17-word bot page, so the regulation text is used instead.

**ACMI, Materials safety** https://acmiart.org/materials-safety (and the near-identical https://acmiart.org/classroom-art-materials-safety)
- verbatim: "Check for the AP Seal on creative products for kids in sixth grade or younger."
- verbatim: "The AP Seal identifies art materials that are certified in a toxicological evaluation by a board certified toxicologist (medical expert) to contain no materials in sufficient quantities to be toxic or injurious to humans, including children".
- verbatim: "Never give children in sixth grade or younger a product with the CL Seal."
- verbatim: "Sometimes a material can have a strong smell (such as a marker) but be non-injurious."
- Supports: child_art_seal values and the AP-only rule. Confidence high (ACMI runs the seal programme; the CFR text confirms the underlying law).

**ACMI, Regulations** https://acmiart.org/regulations
- verbatim: "The law requires a statement on the label of a product with a chronic hazard potential that the product is inappropriate for use by children and permits CPSC to enjoin the purchase of such an art material for use in grades pre-K through 6."
- Supports: why sixth grade is the line. Confidence high.

### Specialist reviewers and enthusiast communities

**JetPens, Ballpoint vs. Rollerball vs. Gel Pens (Internet Archive copy; the live page returned a Cloudflare challenge)**
https://web.archive.org/web/2025/https://www.jetpens.com/blog/Ballpoint-vs.-Rollerball-vs.-Gel-Pens-What-s-The-Difference/pt/167
- verbatim: "Ballpoint pens use viscous, oil-based inks that are usually smudge resistant, quick drying, and water resistant." "Because the ink is so thick, ballpoints work well on low-quality papers with little to no bleedthrough. However, they do require more pressure to write with."
- verbatim: "Hybrid ballpoints have the smooth flow and vibrance of a gel pen and the quick-drying ability and waterproofness of a ballpoint pen."
- verbatim: rollerball "liquid ink ... it'll bleed through lower-quality papers."
- verbatim: gel "tip sizes as small as 0.28 mm"; "gel pens tend to skip more than ballpoints or rollerballs"; "Gel pens also have longer dry times, so they can smudge".
- verbatim: "We've found that Jetstream ink runs out a bit faster than that of other ballpoint pens".
- verbatim: Signo UM-151 "pigment-based formulation is waterproof and resists fading from light exposure"; Vision Elite "ink is fraud resistant and archival".
- Search excerpt (not used): "Oil-based ballpoint ink ranges from roughly 1,000 to 20,000 mPa·s, against water-based ink at 10 mPa·s or less." This would make the ink-thickness ladder numeric, but I never saw it in fetched text, so the ladder is ordinal only.
- Supports: ink_system, trade-offs 1 to 3. Confidence high.

**Goulet Pens, Fountain pen nibs explained** https://www.gouletpens.com/blogs/fountain-pen-blog/fountain-pen-nibs-explained
- verbatim: "These sizes of nibs from Japanese manufacturers like Pilot, Sailor, and Platinum are often ground finer than those from Western manufacturers based in Germany, Italy, France, and the UK."
- verbatim: "Finer nibs put less ink on the paper, so it'll smear less and dry faster." "finer nibs won't feel as smooth as you write".
- verbatim G2 equivalents: "If you like writing with a 0.38 Ultra-fine Pilot G2, you'll like this size" (extra-fine); "If you like writing with a 0.5 extra-fine Pilot G2, you'll like fine nibs"; "If you like writing with a 0.7 Fine Pilot G2, you'll like medium nibs."
- Supports: line_class band mapping, Japanese-nib judgement, fine-line trade-off. Confidence high.

**Goulet Pens, Cartridge/converter compatibility guide** https://www.gouletpens.com/blogs/fountain-pen-blog/cartridge-converter-compatibility-guide
- verbatim: "Many pen brands use their own proprietary style, but there is one common style called Standard International, where many pen makers use the same type of cartridge."
- verbatim table rows (stripped): "LAMY | Proprietary | Proprietary", "Pilot | Proprietary | Proprietary", "Kaweco | Standard International | Standard International".
- Supports: refill_path values. Confidence high.

**Goulet Pens, Why paper matters** https://www.gouletpens.com/blogs/fountain-pen-blog/why-paper-matters
- verbatim: "If it's super absorbent, the fibers of the paper will draw in your ink creating a significant amount of spread, feathering, and bleed through into the backside of the page."
- Supports: liquid-ink paper trade-off, vocabulary (feathering, bleed-through). Confidence high.

### Primers

**Wikipedia, Ballpoint pen** https://en.wikipedia.org/wiki/Ballpoint_pen
- verbatim: "The ball diameter does not correspond to the width of the line produced by the pen. The line width depends on various factors like the type of ink and pressure applied. Some standard ball diameters are: 0.3 mm, 0.38 mm, 0.4 mm, 0.5 mm, 0.7 mm (fine), 0.8 mm, 1.0 mm (medium), 1.2 mm and 1.4 mm (broad)."
- verbatim: "In general, the more viscous the ink, the faster it will dry, but more writing pressure needs to be applied to dispense ink."
- verbatim: hybrid "ink dries faster than a gel pen to prevent smearing when writing. These pens are better suited for left-handed persons."
- verbatim: water-based inks "remain wet longer when freshly applied and are thus prone to 'smearing'—posing problems to left-handed people (or right handed people writing right-to-left script)".
- verbatim: Bic Cristal "the modern pen cap has a small hole at the top to meet safety standards, helping to prevent suffocation if children suck it into the throat."
- Supports: tip_size_mm, quick_dry, the cap judgement. Confidence high.

**Wikipedia, Roller ball pen** https://en.wikipedia.org/wiki/Rollerball_pen
- verbatim: "There are two main types of roller ball pens: liquid-ink pens and gel-ink pens." "liquid inks are limited to dyestuffs".
- verbatim: "Roller ball pens with liquid-ink are more likely to 'bleed' through the paper." "Neither lasts as long as a ballpoint."
- verbatim: "ISO 14145-2 1998: Roller ball pens and refills – Part 2: Documentary use (DOC)".
- Supports: ink_system, trade-offs, gel-versus-rollerball judgement (the disagreement with JetPens). Confidence high.

**Wikipedia, Gel pen** https://en.wikipedia.org/wiki/Gel_pen
- verbatim: "A gel pen uses ink in which pigment is suspended in a water-based gel." "Fraud resistant gel ink is unaffected by solvents such as acetone, and resists check washing."
- Supports: mechanism, permanence. Confidence high.

**Wikipedia, Fountain pen** https://en.wikipedia.org/wiki/Fountain_pen
- verbatim: "The feed makes use of capillary action". "The line width of a particular nib may vary based on its country of origin; Japanese nibs are often thinner in general."
- Supports: mechanism, the Japanese-nib judgement (second source). Confidence high.

**Wikipedia, Marker pen** https://en.wikipedia.org/wiki/Marker_pen
- verbatim: "Today, the ink is usually made on the basis of alcohols". "Markers may be waterproof, dry-erase, wet-erase (e.g. transparency markers), or permanent."
- verbatim: permanent marks "on certain plastics like Teflon, polypropylene etc., ... are not permanent and can be erased easily."
- verbatim: dry-erase "made to be used on a slick (or matte-finished), non-porous writing surface".
- Supports: marker_ink. Confidence high.

**Wikipedia, Highlighter** https://en.wikipedia.org/wiki/Highlighter
- verbatim: "'Gel highlighters' contain a gel stick rather than a felt tip. The gel does not bleed through paper or become dried out in the pen as other highlighters' inks may".
- verbatim: "'Dry highlighters' ... have an applicator that applies a thin strip of highlighter tape".
- Supports: highlighter_format. Confidence medium-high; the "dry mark highlighters ... for highlighting books with thin pages" line supports the Bible-paper question.

### Brand spec pages

**Pentel UK, EnerGel Xm BLN75 and BL80** https://www.pentel.co.uk/product/0-5mm-energel-xm-retractable-rollerball-bln75/ and https://www.pentel.co.uk/product/1-0mm-energel-xm-retractable-rollerball-bl80/
- verbatim: "0.5mm tip gives approx. a 0.25mm (fine) line width"; "1.0mm tip gives approx. a 0.5mm (medium) line width"; "Quick-drying, smooth flowing EnerGel ink is perfect for right or left-handed writers"; "Refillable with item code LRN5".
- Supports: ball-versus-line, brand labels, quick_dry, refill_path. Confidence high.

**STABILO, BOSS ORIGINAL** https://www.stabilo.com/us/products/highlighting/highlighter-stabilo-boss-original-neon-pastel/
- verbatim: "The chisel tip with two line widths of 2 and 5 mm"; "It can be left with its cap off for up to 4 hours without drying or running out."; "water-based ink"; "Refillable with the STABILO BOSS ORIGINAL Refill (not available for pastel colors)".
- The 4-hour cap-off figure is single-source and not in the JSON.

**STABILO point 88** https://www.stabilo.com/us/products/writing/fineliner-stabilo-point-88/
- verbatim: "Fine line width of 0.4 mm". Supports: fineliners are sold by line width.

**STAEDTLER, Permanent markers** https://www.staedtler.com/intl/en/products/markers/permanent-marker/
- verbatim: "With permanent markers, you can write on almost any surface, such as glass, wood, metal and plastic." "Fast-drying: They do not smudge while writing, which makes them excellent for left-handed users as well." "a bullet tip at either end with F (approx. 0.6 mm) and M (approx. 1.5 mm) line width"; "a chisel tip at the other (approx. 1.5 - 4 mm)".

**STAEDTLER, Highlighters** https://www.staedtler.com/intl/en/products/markers/highlighters/
- verbatim: "Good to know: The markers are INKJET SAFE, so will not smudge on inkjet printouts or handwritten text." "The violet and turquoise highlighters are also copy-proof". Range: "Rectangular highlighters with a chisel tip", "triangular highlighters with a fine bullet tip or chisel tip", "Dry highlighters"; product list includes "Textsurfer® gel 264 Gel highlighter" and "Textsurfer® dry 128 64 Triangular highlighter pencil". Refill: "ready to write again in three to four hours."

**STAEDTLER, Artist fineliners** https://www.staedtler.com/intl/en/products/art-supplies-materials/artist-fineliners-drawing-pens/
- verbatim: "pigment liner black in assorted line widths (0.05, 0.1, 0.3, 0.5, 0.7, 1.0, 1.2, 0.3-2.0)".

**uniball brand store (Shopify JSON for the 207 and POSCA collections)** https://www.unibrands.co/collections/207, https://www.unibrands.co/collections/posca
- verbatim: 207 "uni Super Ink™ – Fraud-resistant ink bonds with paper to help protect against check washing, water, fading, and document alteration".
- verbatim: refill "not compatible with 207 IMPACT pens".
- verbatim: 207 Plus "super-enhanced smoothness, drying speed and line intensity".
- verbatim: POSCA "permanent on porous surfaces and removable on most non-porous surfaces"; "water-based pigment".

**Pilot Pen Europe, FriXion** https://www.pilotpen.eu/frixion
- verbatim: "The unique gel ink responds to the heat generated by the rubbing out"; "Because of the erasable ink, FriXion Ball must not to be used for signatures, legal documents, examination papers or other documents where writing needs to be of a permanent nature."
- Wikipedia, Pilot (pen company): "FriXion (erasable ink gel pens, highlighters, and stamps)", which is why permanence stays relevant on the highlighting branch.

### Retail listings (what data is already present)

**Cult Pens (UK specialist retailer; Shopify product JSON)** e.g. https://cultpens.com/products/pilot-g2-05-gel-ink-rollerball-pen-blg205
- verbatim: G2 05 "0.5mm ball writes a 0.32mm line."; V5 RT refill "Extra-Fine - 0.5mm ball writes a 0.25mm line."; FriXion Point refill "0.5mm tip writes approx. 0.35mm line."; Jetstream SXN-150 "1.0mm ball writes a 0.45mm line." and "Very popular with left-handed writers."
- verbatim: Pigma Micron "01 - 0.25mm", "03 - 0.35mm", "05 - 0.45mm", "08 - 0.5mm"; "Archival quality ink is acid-free, chemically stable, waterproof, and fade resistant."
- verbatim: Sharpie Fine "permanently marks most surfaces including glass, metal, photos, foil and most plastics"; "approx. 1mm line width".
- verbatim: LAMY safari "Use Lamy T10 cartridges, or the optional Lamy Z28 converter available separately, for bottled ink."
- Structured tags seen: `Ink_Type` (Gel Ink, Liquid Ink, Hybrid Ink, Erasable, Waterproof Ink), `Tip_Size` (fountain grades), `Tip_Type` (Ball, Porous, Fountain Pen), `Refill_Type` (Refillable, Disposable, Fountain Pen Ink Cartridge, Bottled Ink), `Advanced_Mechanism` (Capped, Retractable), `Sub_Category`. ~~Note Cult Pens tags the EnerGel refill as Liquid Ink~~ Corrected 2026-10-25: Cult Pens tags the LRN5 refill and the EnerGel Xm, X and Plus as `Gel Ink`; only the 0.7 needle-tip refill and EnerGel Permanent are `Liquid Ink` (checker, confirmed in `check-pens/cp_pentel-lrn5-gel-ink-refill.json`: "Pentel LRN5 Gel Ink Refill ['Ink_Type:Gel Ink']"). EnerGel is back in the gel-rollerball example.
- The pages behind `cultpens_listings` (the reference URL can hold only one): https://cultpens.com/products/pilot-g2-05-gel-ink-rollerball-pen-blg205, https://cultpens.com/products/pilot-bxsv5rt-rollerball-pen-refill, https://cultpens.com/products/pilot-bls-frp5-frixion-point-pen-refill-pack-of-3, https://cultpens.com/products/uni-jetstream-sport-sxn-150-rollerball-pen, https://cultpens.com/products/sakura-pigma-micron-drawing-pen-01, https://cultpens.com/products/sharpie-permanent-marker-fine-assorted-set-of-12, https://cultpens.com/products/lamy-safari-fountain-pen-black, https://cultpens.com/products/pentel-lrn5-gel-ink-refill, https://cultpens.com/products/pentel-energel-0-7-rollerball-pen-refill.
- Retailer contradiction kept: the V5 RT pen page says "0.5mm ball writes a 0.3mm line" while its BXSV5RT refill says 0.25 mm (checker). Both are inside the 45 to 70 percent range; the table uses the refill.

**Amazon.com search "gel pens" (one results page fetched; later queries returned a 1.3 KB bot page and I stopped)** https://www.amazon.com/s?k=gel+pens
- verbatim titles: "Sharpie S-Gel Gel Pens, Black Barrel, Medium Point (0.7mm), Black Gel Ink, 12 Count ..."; "PILOT G2 Premium Gel Pens, Fine Point 0.7mm, Black Ink, 12-Pack"; "Piochoo Gel Pens, Retractable Black Ink Pens Quick Dry,10 Pack"; fragments "Retractable, Faster-Drying, Smooth Writing, Smear-Resistant, uni Super Ink™ Plus+" and "Smooth Writing, Fraud-Resistant, uni Super Ink™".
- What this tells the scraper: gel-pen titles carry ink type, point word plus mm, pack count, and often quick-dry and fraud-resistant claims. I could not see Amazon titles for highlighters, markers or fountain pens. `ink_system`, `tip_size_mm`, `marker_ink`, `tip_shape` and `highlighter_format` are marked `listing` on the evidence of Amazon gel titles plus brand and Cult Pens titles that put the type and tip in the product name; that is medium confidence for the non-gel families. `permanence`, `quick_dry`, `refill_path` and `child_art_seal` are marked `researched`.

### Could not reach
- CPSC art-materials guidance page (bot page). Replaced by the regulation text.
- ISO 27668-2 (gel pens, documentary use) on iso.org (3-word response). The gel DOC standard is therefore not cited; only ballpoint (ISO 12757-2, read) and rollerball (ISO 14145-2, via Wikipedia) DOC are.
- JetPens live pages (Cloudflare); the Internet Archive copy was used, then the Archive went offline mid-run, so no further archive copies.
- Sharpie, BIC and Schneider brand sites (403, 404 or no response). Schneider and BIC publish write-out lengths, which is what the dropped cost-per-metre metric needed.
- Web search: the session's search budget (200) was exhausted after four searches in this run; all later sources were found by browsing brand and retailer sites directly.

### Sources added after the blind check (2026-10-25, scratchpad `fix-pens/`)

Web search was exhausted (200 of 200), so these were found by browsing; all quotes verbatim from curl plus HTML stripping or Shopify product JSON.

**Copic official, What is Copic?** https://copic.jp/en/about/
- verbatim: "First released in 1987 as a drawing tool for designers, the “Copic” marker (now known as “Copic Classic”) quickly gained recognition"; "Copic products, including alcohol-based markers, are sold in over 70 countries"; "Copic alcohol markers offer a complete range of products".
- Supports: alcohol markers are a paper art family (second source with Wikipedia, Marker pen: "In 1987 Copic Sketch markers were released, further popularising markers for professional illustration").

**Cult Pens art and marker pages (`cultpens_art`; Shopify JSON)**
- Copic Sketch https://cultpens.com/products/copic-sketch-marker-pen: "Copic Sketch Marker is the leading professional graphics marker"; "a dynamic double ended alcohol-based marker"; "the favourite marker of countless artists and designers". Tag `Ink_Type:Alcohol Based`.
- Winsor & Newton ProMarker https://cultpens.com/products/winsor-newton-promarker: "Markers contain alcohol-based, translucent ink which is blendable"; tags `Ink_Type:Alcohol Based`, `Sub_Category:Graphic Markers`, `Refill_Type:disposable`.
- Tombow ABT Dual Brush https://cultpens.com/products/tombow-abt-dual-brush-pen: "Tombow ABT's are water-based and so odourless, non-toxic and acid free. They work like watercolour paints and blend effortlessly." Tags include both `Ink_Type:Alcohol Based` and `Ink_Type:Liquid Ink`: a retailer tag that contradicts the description, noted in art_marker_ink.
- Giotto Turbo Giant https://cultpens.com/products/giotto-turbo-giant-super-washable-fibre-pens-conical-tip-nib-7-5mm-assorted-colours-144pcs: "Easily washable"; tags `For Kids`, `Sub_Category:Colouring Pens`. (The author's Crayola washable capture was a 404; Wikipedia, Crayola: "a line of washable markers were added in 1987".)
- edding 4095 https://cultpens.com/products/edding-4095-chalk-marker-bullet: "Contains highly opaque water-based liquid chalk, suitable for use on blackboards, mirrors and glass." "Removable with a damp cloth." Tag `Ink_Type:Chalk`.
- Schneider Slider Memo XB https://cultpens.com/products/schneider-slider-memo-xb-ballpoint-pen: "Hybrid Viscoglide ink"; "extra-broad 1.4mm tip".
- Paper Mate Flexgrip Elite https://cultpens.com/products/paper-mate-flexgrip-elite-ballpoint-pen: "the broad 1.4mm ball tip (0.8mm line)".

**MyBinding, What are some good chalkboards?** https://www.mybinding.com/a/knowledge-base/chalkboards/what-are-some-good-chalkboards
- verbatim: "liquid chalk markers — pen-format markers filled with water-soluble chalk-based ink"; "Liquid chalk markers work on most smooth chalkboard surfaces".
- Supports: liquid chalk value (second source with edding).

**Already captured, newly used**
- Pilot Pen Europe FriXion (`pilot_frixion`, author capture `pens/pilot_eu_frixion.txt`): "0.7mm tip gives a 0.35mm medium stroke width." With Goulet's "0.7 Fine Pilot G2", Pilot itself labels 0.7 mm Fine on one pen and medium on another; replaces the Sharpie example.
- Wikipedia, Marker pen: "Wet-wipe markers —or wet-erase markers—are another version that are used on overhead projectors, signboards, whiteboards, and other non-porous surfaces."
- Wikipedia, Roller ball pen: "Most roller ball refills comply to the ISO 14145-2:1998 standard and are approved for documentary use."
- 16 CFR 1500.14(b)(8): "pencils and pens intended specifically for sketching and drawing are likely to be art materials".
- ISO 11540:2021 introduction: "it is not possible to identify with certainty any writing instruments with detachable caps that would never be accessible to children"; adult-only products "must be clearly labelled to that effect".
- Cult Pens G2 05: "archival acid-free ink" on an ordinary gel pen.
- JetPens: gel and Jetstream "tip sizes as small as 0.28 mm", the second source for the bottom of the ball-size range.

## Data points used for derived metrics

`approx_line_mm` (ball pens only):

| Pen | Ink | Ball mm | Stated line mm | Line / ball | Source |
|---|---|---|---|---|---|
| Pentel EnerGel Xm BLN75 | liquid gel | 0.5 | 0.25 | 0.50 | Pentel UK |
| Pentel EnerGel Xm BL80 | liquid gel | 1.0 | 0.5 | 0.50 | Pentel UK |
| Pilot G2 05 | gel | 0.5 | 0.32 | 0.64 | Cult Pens |
| Pilot V5 RT refill | liquid | 0.5 | 0.25 | 0.50 | Cult Pens |
| Pilot FriXion Point refill | erasable gel | 0.5 | 0.35 | 0.70 | Cult Pens |
| uni Jetstream SXN-150 | hybrid | 1.0 | 0.45 | 0.45 | Cult Pens |
| Pilot FriXion Ball 0.7 (added 2026-10-25) | erasable gel | 0.7 | 0.35 | 0.50 | Pilot Pen Europe |
| Paper Mate Flexgrip Elite (added 2026-10-25) | ballpoint | 1.4 | 0.8 | 0.57 | Cult Pens |

Range 0.45 to 0.70, four of eight at 0.50. Three independent publishers (Pentel, Pilot, Cult Pens). Wikipedia's "ball diameter does not correspond to the width of the line" is the third, qualitative, source. Fineliners are excluded because they state the line, not a ball.

`line_class` bands, revised 2026-10-25 to leave no gaps (our mapping, confidence medium): tiny = ball under 0.45 mm (0.3, 0.38, 0.4), fountain EF, fineliner under 0.3 mm (0.05 to 0.25, so Pigma 01 at 0.25 is tiny); everyday = ball 0.45 to under 0.9 mm (0.5, 0.7, 0.8), fountain F or M, fineliner 0.3 to under 0.6 mm; bold = ball 0.9 mm and up (1.0 to 1.4), fountain B or broader, fineliner 0.6 mm and up (STAEDTLER 0.7, 1.0, 1.2). Sourced: only Goulet's 0.38 to EF, 0.5 to F, 0.7 to M. Ours: the 0.45 and 0.9 mm cut-offs (midpoints between Wikipedia's standard sizes), bold as B, and all fineliner edges, set from the 0.45 to 0.70 ratio (a ball under 0.45 writes about 0.14 to 0.31 mm; 0.45 to 0.9 writes about 0.2 to 0.63 mm; 0.9 and up writes 0.4 mm and more). The old notes capped tiny fineliners at 0.2 mm while saying a 0.38 ball writes up to 0.27 mm; the new 0.3 mm edge removes that contradiction.

## Against the existing add-on schema

Add-on read: `supplies/stationery/add-ons/pen.jsonc` is empty (`{}`), and `stationery-standard.jsonc` is also empty ("no shared block has earned a field yet"). The composed schema is therefore only `supplies-standard.jsonc`: `high_signal_markdown` and the `sizing` block (size_stated, pack_count, pieces_included_text, dimensions, capacity, weight, measurements_text). The sibling `ink_cartridge.jsonc` already has `tip_size_raw` and `compatibility_raw`, which this proposal mirrors from the pen side.

| Facet in this doc | In add-on today | Proposed kind under AGENTS.md | Note |
|---|---|---|---|
| job | no | not stored (taxonomy or derived from title) | Each family may deserve its own leaf; until then derive at query time. |
| ink_system | no | vertical anchor / hard filter: `ink_system: enum [ballpoint, hybrid_ballpoint, gel, liquid_rollerball, fountain, porous_tip, not_applicable]` | The mechanism; in titles; commit to augmenting. |
| tip_size_mm | no | category quality currency: `tip_size_mm: number`, plus `tip_size_basis: enum [ball_diameter, line_width, nib_grade]` | Without the basis the number is not comparable. Keep `tip_size_label_raw` out: the word label is noise. Variant-dependent (one listing in 0.5 and 0.7), so it lives inside `sizing` by rule 2. |
| nib grade (inside line_class) | no | hard filter for fountain pens: `nib_grade: enum [ef, f, m, b, stub_italic, other]`, inside `sizing` | Variant-dependent like tip size. |
| line_class | no | derived, not stored | From tip_size_mm, tip_size_basis and nib_grade. |
| permanence | no | hard filter: `ink_permanence: enum [erasable, standard, waterproof_fade_resistant, document_grade, unspecified]` | Rule 5 cuts curated claim vocabularies; this survives because buyers filter on it literally (cheques, contracts) and erasable is a hard exclude. If that is judged too claim-like, it goes to high_signal_markdown. |
| quick_dry | no | high_signal_markdown | A brand claim with no common test; worth a line, not a column. |
| refill_path | no | hard filter: `refill_system: enum [disposable, brand_refill, standard_international_cartridge, proprietary_cartridge, bottled_ink, marker_refill_ink]` plus `refill_code_raw: string` | Lock-in and running cost; mirrors `compatibility_raw` on the refill sibling so the two can be joined. |
| marker_ink | no | hard filter: `marker_ink: enum [water_based, permanent_alcohol_solvent, dry_erase, wet_erase, paint, chalk, not_applicable]` | Decides surface. |
| tip_shape | no | none (visual) | Rule 1: the photo answers chisel versus bullet. |
| highlighter_format | no | hard filter: `highlighter_format: enum [liquid, gel_stick, dry, not_applicable]` | Gel versus liquid is not reliable from a photo. |
| child_art_seal | no | high_signal_markdown | Rule 5 cuts certifications. It is the child-safety filter, though, so the markdown line should name AP or CL verbatim and the ranker should be told to read it. |
| cap safety (ISO 11540, judgement only) | no | none | Not on listings; covered by the judgement. |

Fields this register considers noise for pens: `sizing.dimensions`, `sizing.capacity` and `sizing.weight` (a photo answers pen length; ink volume is almost never stated and not comparable across ink types); `measurements_text`. `pack_count` is useful and stays (packs of 3 to 36 are the norm on the Amazon page).

## Branches

The `when` values on every branch are values of the split facet, and the split questions offer those values directly (with the stated rule that a "ballpoint" answer covers ballpoint and hybrid ballpoint, and "everyday" maps to permanence "standard").

**Split 1, job ("Writing, fine drawing, colouring, marking objects or boards, or highlighting?")** (revised 2026-10-25: fifth value `colouring or art markers`, two WEAK legs removed, art_marker_ink added)

- when `writing`: then_ask ink_system, line_class, permanence; makes_irrelevant marker_ink, tip_shape, highlighter_format.
  - ink_system: its definition is "The ink and delivery system of a writing pen".
  - line_class: its definition gives bands for ball pens and fountain nibs.
  - permanence: "Document-grade ink is tested to stay visible after water, light, bleach and erasure" (permanence, why experts care) concerns written lines.
  - marker_ink irrelevant: defined as "The ink base of a marker for objects or boards". art_marker_ink irrelevant: defined as "The ink of a colouring or art marker". tip_shape irrelevant: defined as "The shape of a marker or highlighter tip". highlighter_format irrelevant: defined for highlighters only.
- when `fine drawing or lettering`: then_ask line_class, permanence; makes_irrelevant highlighter_format.
  - line_class: its definition includes "fineliner up to 0.2 mm" and "fineliner 0.3 to 0.5 mm".
  - permanence: "Pigment fineliners such as Pigma Micron are sold as waterproof and fade resistant" (permanence, why experts care).
  - highlighter_format irrelevant by definition. The marker_ink irrelevant leg was removed after the blind check (WEAK: fineliners and markers share the porous-tip mechanism, and no source says ink base stops mattering). Brush pens now go to `colouring or art markers`.
- when `colouring or art markers` (added 2026-10-25): then_ask child_art_seal, art_marker_ink, tip_shape; makes_irrelevant ink_system, marker_ink, highlighter_format.
  - child_art_seal: ACMI "Check for the AP Seal on creative products for kids in sixth grade or younger"; 16 CFR 1500.14: multi-colour marker packs "are likely to be art materials".
  - art_marker_ink: Giotto "Easily washable" children's fibre pens; Tombow ABT "water-based ... blend effortlessly"; Copic and ProMarker "alcohol-based" (Cult Pens, Copic official).
  - tip_shape: Copic Sketch "a flexible brush nib at one end and an angled chisel nib at the other"; ProMarker "a fine bullet tip at one end and a broad chisel tip at the other".
  - ink_system irrelevant: defined for writing pens. marker_ink irrelevant: defined for markers for objects or boards; art_marker_ink carries the ink choice here. highlighter_format irrelevant by definition.
- when `marking objects or boards`: then_ask marker_ink, tip_shape; makes_irrelevant ink_system, art_marker_ink, highlighter_format.
  - marker_ink: "The ink base of a marker, which decides the surfaces it marks".
  - tip_shape: "A bullet gives an even line for labels. Double-ended markers pair them" (tip_shape, why experts care).
  - ink_system irrelevant: defined for writing pens. art_marker_ink irrelevant: defined for colouring markers. highlighter_format irrelevant by definition. The line_class irrelevant leg was removed after the blind check (WEAK: STAEDTLER sells the same Lumocolor in F 0.6 mm and M 1.5 mm, so width matters; line_class's bands just do not cover markers, and tip_size_mm stays as an annotation).
- when `highlighting`: then_ask highlighter_format, tip_shape; makes_irrelevant ink_system, marker_ink, art_marker_ink, line_class.
  - highlighter_format: by definition. tip_shape: "A chisel highlights a full line of text and underlines with its edge: STABILO BOSS gives 5 mm and 2 mm."
  - irrelevant legs: ink_system, marker_ink and art_marker_ink by definition; line_class as for markers (highlighter strokes are 2 to 5 mm).
  - permanence was removed from this branch's makes_irrelevant before publishing: Pilot makes FriXion erasable highlighters (Wikipedia, Pilot), so erasable versus permanent still applies.

**Split 2, ink_system ("Ballpoint, gel, felt tip, or fountain pen?")** (question revised 2026-10-25; new value `felt tip` has no branch, since no source says it changes the next question. A "gel" answer covers gel and liquid rollerball, which share a branch.)

- when `ballpoint` or `hybrid ballpoint`: makes_irrelevant quick_dry.
  - "Oil ballpoint and hybrid inks already dry fast, so the claim only separates gel and liquid pens" (quick_dry, why experts care), from Wikipedia ("the more viscous the ink, the faster it will dry"; hybrid "dries faster than a gel pen") and JetPens ("quick drying").
- when `gel` or `liquid rollerball`: then_ask quick_dry.
  - "Water-based gel and liquid inks stay wet longer, which smears under a left hand or right-to-left script" (quick_dry, why experts care; Wikipedia verbatim above).
- when `fountain`: then_ask refill_path.
  - "A fountain pen that takes standard international cartridges accepts many brands' ink; a proprietary one (LAMY, Pilot) takes only its own cartridges or converter" (refill_path, why experts care; Goulet table).
  - A makes_irrelevant quick_dry leg on this branch was dropped before publishing: fountain ink is liquid, and its dry time depends on the bottled ink and the nib (Goulet: finer nibs "dry faster"), so the facet is not irrelevant, only rarely claimed.

**Splits 3 and 4 (line_class, permanence)**: no branches (unchanged after the blind check; permanence became ordinal, which changes how it filters, not what comes next). Neither answer changes which other facets matter; "erasable" could exclude document grade, but that is the split facet itself.

## Trimmed detail

- **mechanism.plain** (152 to 150 words): "metal" in "split metal nib"; "ballpoint" in "Hybrid ballpoint ink"; ", and the ink's" became "; the ink's". No fact cut.
- **highlighter_format.why_experts_care**: "Liquid fluorescent ink is the brightest" was cut before publishing because no read source ranks brightness; "uncapped" was cut from the gel claim because Wikipedia says only that gel does not dry out "in the pen".
- **marker_ink.why_experts_care**: "and is what children's and washable markers use" cut; washable markers are real but I found no fetched source describing them beyond a Crayola history line ("a line of washable markers were added in 1987", Wikipedia, Crayola).
- **quick_dry.why_experts_care**: "stay wet for seconds" became "stay wet longer" (the seconds figure was a search excerpt); "close most of the gap" cut as unsourced.
- **permanence**: "Artists need waterproof pigment to ink under watercolour" replaced with the Pigma Micron claim actually read. The split rationale lost "pigment inks are a minority of gel and fineliner ranges" (unsourced).
- **splits[0].rationale**: "removes three quarters of the catalog" became "sets aside three families" (no catalog counts were available).
- **splits[2].rationale**: "cuts each ink family into roughly thirds" cut (unsourced).
- **ink_system.backfill_note**: Pentel EnerGel dropped from the "gel rollerball" example, since Cult Pens tags EnerGel as liquid ink and Pentel calls it a rollerball. (Wrong premise; reversed 2026-10-25, see below.)
- Single-source figures kept here only: STABILO BOSS "up to 4 hours" cap-off; STAEDTLER Textsurfer refill "three to four hours"; ISO 11540 3,4 mm² single-orifice note.

## Corrections

1. `vertical` is `other`, not `supplies` as the brief asked. The skill's `schema.json` restricts `vertical` to formulations, machines, fashion, furnishing and other, so `"supplies"` failed validation ("'supplies' is not one of [...]"). The brief also says not to modify the scripts or schema and that validate must run clean, so `other` is the only value that satisfies both. Every Supplies leaf in this batch will hit the same error; the schema enum needs `supplies` added, after which this field should be changed back.
2. Two branch legs removed before publishing (highlighting makes permanence irrelevant; fountain makes quick_dry irrelevant); reasons under Branches.
3. Five prose claims rewritten or cut before publishing because no read source supported them; listed under Trimmed detail.

## Corrections after the blind check (2026-10-25)

Report: `check.md` (13 required fixes). All 13 accepted; none rejected. Every new quote is under "Sources added after the blind check".

1. Fix 1: `job` gains a fifth value, `colouring or art markers`, so children's washable markers, water-based brush pens and alcohol markers have a home; question now "Writing, fine drawing, colouring, marking objects or boards, or highlighting?" (10 words).
2. Fix 1: new facet `art_marker_ink` (washable, water-based, alcohol-based; "Washable for kids, water-based brush pens, or alcohol markers?"), sourced to Copic official, Cult Pens (Copic, ProMarker, Tombow ABT, Giotto) and Wikipedia.
3. Fix 1: new job branch `colouring or art markers`: then_ask child_art_seal, art_marker_ink, tip_shape; makes_irrelevant ink_system, marker_ink, highlighter_format. art_marker_ink added to makes_irrelevant on the writing, marking and highlighting branches.
4. Fix 1: marker_ink is now scoped to markers for objects or boards; alcohol art markers for paper no longer pass through the surface question. Mapping now keeps both water-based and permanent for a "paper" answer.
5. Fix 1: mechanism.plain says alcohol is also for "blended art colour" (cut "the ink's thickness sets how it writes" to stay under 150 words); porous family typical_for adds colouring.
6. Fix 2: line_class bands made contiguous (ball <0.45 / 0.45 to <0.9 / ≥0.9 mm; fineliner <0.3 / 0.3 to <0.6 / ≥0.6 mm; EF / F or M / B or broader). backfill_note says only Goulet's EF/F/M links are sourced; the cut-offs, B, and fineliner edges are ours.
7. Fix 3: permanence is now `ordinal` and filters at or above the answer, so document grade meets a "waterproof" answer.
8. Fix 3: dropped the "archival → waterproof" rule (Cult Pens calls the G2 archival); "archival" removed from listing_field_hint and skip_if_known.
9. Fix 3: permanence backfill_cost low → medium. Document grade defined as claimed ISO DOC or fraud resistance, and an untagged pen is unknown because Wikipedia says most rollerball refills meet ISO 14145-2. The "'Archival'..." judgement is reworded and cites wiki_rollerball.
10. Fix 4: ISO 11540 judgement restated to cover pens "children up to 14 may foreseeably use", not those "sold for children"; the note gives the labelled adult-only exception. iso11540_2021 supports line updated.
11. Fix 4: child_art_seal why_experts_care, definition and backfill_note add LHAMA's sketching-and-drawing pens and multi-colour marker packs; cfr_1500_14 gains a supports line; the LHAMA judgement note updated.
12. Fix 5: approx_line_mm depends_on adds `job`. The formula names the ball inks and says to use tip_size_mm as is when it states a line width. tip_size_mm backfill_note says to store whether the number is a ball diameter or a line width.
13. Fix 6: ink_system question → "Ballpoint, gel, felt tip, or fountain pen?" (no "liquid rollerball"; a "gel" answer covers both water-based ball inks). New value `felt tip`. backfill_note places dip pens under fountain and multi-pens under their refills' ink, and says hybrids need a model lookup. listing_field_hint says title words are unreliable. The split rationale no longer claims the ink type is in the title.
14. Fix 7: marker_ink gains `wet-erase` (Wikipedia, Marker pen) and `liquid chalk` (MyBinding, edding via Cult Pens). Question → "Paper, whiteboard, chalkboard, glass and plastic, or craft painting?"; vocabulary adds Wet-erase and Liquid chalk.
15. Fix 8: removed both WEAK legs (fine drawing → marker_ink irrelevant; marking → line_class irrelevant). I did not add a marker-width question: tip_size_mm is not novice-answerable, and no source maps marker widths to words.
16. Fix 9: tip_size_mm.range now reads "Ball sizes run from about 0.3 mm to 1.4 mm", with "common steps" dropped. Sources: Wikipedia, JetPens 0.28 mm, and Cult Pens 1.4 mm Schneider and Paper Mate. listing_field_hint says markers often give only a word and fountain pens a nib letter.
17. Fix 10: the Sharpie "0.7 mm Medium" example is replaced by Pilot's own labels: G2 0.7 Fine (Goulet) against FriXion "0.7mm tip gives a 0.35mm medium stroke width" (Pilot). This applies to line_class why_experts_care, the split rationale and the point-words judgement. amazon_gel_search is no longer evidence for line_class, and its supports line no longer names Sharpie.
18. Fix 11: overlap rules for crafts `paint`, crafts `brush-stamp-tools`, `pencils` and play `play-dough` are stated in job.backfill_note and in the Scope paragraph above.
19. Fix 12: the EnerGel tagging claim is corrected (LRN5 and Xm/X/Plus are `Gel Ink`), and EnerGel is restored to the gel-rollerball example in ink_system.backfill_note. The Cult Pens URLs behind `cultpens_listings` are listed under Retail listings, and the reference title is updated.
20. Fix 13: listing_field_hint for marker_ink, tip_shape and highlighter_format now says the evidence is brand pages and Cult Pens, and marketplace titles are untested or unconfirmed. highlighter_format backfill_note says the dry half is weak (Wikipedia: "sometimes advertised").
21. Also: approx_line_mm now rests on eight pens from three publishers, after adding FriXion 0.7 → 0.35 (Pilot) and Paper Mate 1.4 → 0.8 (Cult Pens). The 45 to 70 percent range is unchanged.
22. Also: new judgement (medium, ours): both alcohol and water-based art markers are sold as blendable, so blending alone does not choose between them. New references: `cultpens_art`, `copic_official`, `mybinding_chalk`. Vocabulary adds Felt tip and Alcohol marker.
23. Not changed: the checker's side notes on `tip_shape` value "fine" mixing size with shape and on `quick_dry` arguably being `listing` were not required fixes and are left as they were.