Fountain Pen Ink Alchemist

A 60 ml bottle of ink lasts most people two years. So when a pen skips, an ink feathers, or a favorite shade is discontinued, the fix isn't buying more ink — it's adjusting what you have: a measured splash of distilled water, a drop of glycerin, a logged ratio you can reproduce (or never repeat). The failure modes are all un-measured: too much water turns the ink watery-pale, too much glycerin smears for an hour, and a homemade dye mix grows mold in the feed within a fortnight. This skill does the arithmetic and keeps the rules (pigment ≠ dye, acrylic = pen death) in front of you at the moment of mixing.

When to Use

• Ink too dry / pen skips → compute the right dilution instead of pouring blind (5-25% water is the useful band; 30%+ is ruined)
• Estimating how a dilution or glycerin addition changes dry time on YOUR paper at YOUR humidity
• Logging every custom batch (components, ratio, verdict) so a happy accident is reproducible — ink_log.json is the lab notebook
• Deciding between ink classes for a pen: dye vs iron-gall vs pigment vs shimmer — nib width drives the answer
• Converting recipe drops to ml and ml to fills/pages for a given nib
• Tempted by acrylic/India/calligraphy inks in a fountain pen — stop, read the safety section, use a dip pen instead

Not for: rehydrating dried-out bottles of unknown provenance, vintage ink restoration chemistry, or anything involving solvents — those need dedicated references.

The Method

# The core move: dilute 60 ml by 15% and see everything that changes
python3 scripts/ink_alchemy.py mix --target-ml 60 --add-water-pct 15

# With the dry-time modifiers: 3% glycerin, humid summer office
python3 scripts/ink_alchemy.py mix --target-ml 60 --add-water-pct 10 \
    --glycerin-pct 3 --rh 70

# Log the batch you just made (ratios + verdict notes)
python3 scripts/ink_alchemy.py batch add --name "misty ku-jaku" \
    --components "ku-jaku 50ml, distilled water 10ml" --ratio "5:1" \
    --notes "wet flow, dry EF finally happy; shade one step lighter"
python3 scripts/ink_alchemy.py batch list

# Compare two ink classes before committing a pen to one
python3 scripts/ink_alchemy.py compare shimmer pigment
python3 scripts/ink_alchemy.py compare --list

# Recipe math: drops in the recipe, ml in your pipette
python3 scripts/ink_alchemy.py convert --drops 20 --nib f
python3 scripts/ink_alchemy.py convert --ml 30 --drop-ml 0.05
python3 scripts/ink_alchemy.py convert --nib-table

Dilution Quick Reference

Dry time ≈ base × (volume ratio)^0.85 × 1.18^(glycerin %) × 2^((RH−50)/40). Doubling from 50% to 90% humidity roughly doubles dry time — a mix that behaved in winter smears all August.

Ink Class Rules (the part that saves pens)

The mechanism matters: dye molecules stay dissolved and flow through a 0.2 mm EF slit; pigment and mica are solids that settle and accrete in the feed channel and under the nib tines. A clogged feed means disassembly or a parts sink — an hour of surgery to save 15 minutes of flushing.

Common Pitfalls

1. Tap water instead of distilled. Minerals crust the nib tipping and feed, and tap microbes jump-start mold. Distilled only.
2. Shaking a shimmer bottle. Shaking whips in air bubbles that cause hard starts; swirl gently, bottle vertical.
3. Pigment ink left in an unused pen. Water evaporates through the cap in weeks; the solids stay and cement the feed. Flush any pen that sits for more than a week.
4. Glycerin as a universal flow agent. It's a humectant — past ~5% it keeps the line wet enough to smear on coated paper for an hour. 1-3% is the working range.
5. Homemade dye ink with no biocide. Water + dye + no preservative is a microbial culture; mold hyphae physically clog the feed. If it smells sweet or earthy, discard the batch and flush the pen.
6. "Just a little" acrylic or India ink. There is no little. Shellac and acrylic binder dry insoluble inside the feed; the pen is often not recoverable. Dip pens exist for these inks.
7. Mixing in the pen instead of a vial. You can't measure, can't log, and can't undo. Always mix in a clean vial, then fill.

Verification Checklist

• Distilled water used (not tap, not filtered)
• Dilution computed with mix — volume, ml to add, new total recorded
• Mix made in a clean vial, not inside the pen
• Swab/scratch test on the actual target paper, both wet and dry
• Batch logged: components, ratio, date, verdict notes
• Pen flushed before filling and scheduled for flush (4-6 wk dye, weekly pigment/shimmer)
• No acrylic/India/solvent ink ever contacted the fountain pen
• Shimmer only in broad/stub; swirl not shake

Maintenance Cadence (flush before it's a problem)

A pen that writes fine is not evidence the feed is clean — it's evidence it's clean today. Flushing is 60 seconds under the tap followed by a converter of clear water; disassembly is an hour with a parts sink. The cadence table is the whole trick.

References

• references/ink-craft.md — the deep version: water-ink ratio effects, drying physics (glycerin, surfactants, humidity), why inks mold and preservative reasoning, dye vs pigment mechanics, pH, classic recipes, the batch log schema, and the full safety rules.