# Copperplate Engraving — Style Prompt

> An intaglio plate that engraves itself: a burin cuts swelling lines into copper, a proof is pulled, and the figure builds up — outline, hatching, cross-hatching — until engraved lettering, magnified details and a hand-laid wash make a finished plate.
> References (grammar only): 19th-century natural-history plates — Haeckel, Audubon, Westwood, the *Britannica* copperplates (centred subject, numbered roundels, roman title over an italic name, "del." / "sculp." credits, the plate mark); Hogarth and Doré for the burin line (hatching that follows the form, crossing only in half-tones); hand-coloured plates for washes laid after printing. Never copy a plate, pose, border or title.

## 1. Essence, and what it is not

An **intaglio print**: the line is ink held in a groove a burin cut into copper. Three rules:

1. **Tone is made of lines, never of fills.** Light is bare paper; half-tone is one family of parallel lines; shadow a second family crossing it; the deepest dark a third, lozenge-making family. No grey fill anywhere in the ink.
2. **Every line swells and tapers.** The burin enters fine, bites deeper mid-run and lifts out to a point. Lines thicken where the form turns from the light and vanish where it faces it; contours are cut in several runs and thin where runs hand over. A uniform-width line reads as a pen or vector drawing — never.
3. **Colour comes afterwards, by hand**: transparent watercolour laid flat region by region over the finished black print, spilling past the lines, pooling at its edges, ink always on top. A film may stay monochrome long; colour arriving is an event.

Not a woodcut (black block, white gouges — `woodcut`), not a pen sketch (loose broken lines — `urban-sketch`), not an engineering drawing (`blueprint`), not a sepia filter.

## 2. Materials & rendering

- **The sheet is the world**: 1920×1080 world units of laid paper (cream, ~`#f1e8d2`) with world-space texture (fibres, laid lines, sparse foxing) that zooms with the camera; a pressed, bevelled **plate mark** and a ruled border (rule + hairline) frame it.
- **Ink** is one warm near-black (~`#1c1510`). Width ratios: outlines heaviest (swelling ×0.45–1.35), first hatching from a hair (~0.18 px) to ~2 px, crossing ~0.8×, third family ~0.6×, hair and stipple finest. Spacing is **relative to the figure** (~1/180 of its height, a little wider per later family) so small figures never go grey.
- **Swell law** for every hatch line: width × (0.2 + 0.8·sin(πu)^0.7), tapered over its first and last ~22 %. Families switch on by tone thresholds (~0.14, ~0.5, ~0.75 on a 0–1 tone).
- **One light direction** for the whole film (upper left by convention); heavier outlines away from it; tone fields come from the shape (pillow lighting, analytic spheres and cylinders), never from texture. **Occlusion** is geometric: lines stop at the shapes in front.
- **Roundels**: double-ruled circle, ruled-machine ground with a white halo round the subject, content authored at a large radius and scaled in. **Leaders**: hairlines from a dot on the part to the rim, routed with clearance, a small italic figure number at the root.
- **Hand colouring** multiplies over paper and under ink: a few px of spill, slight misregister, tide-line at the wet edge, low-frequency density lift, occasional backruns, granulation; each region blooms from where the brush touched.
- **Copper** (when shown): polished warm metal, polishing hairlines, a soft reflected window; grooves = dark trough + bright burr toward the light. The **burin** (lozenge steel shaft, bevelled face, mushroom handle) is held low and turned ≤ 15° off the line so the fresh groove shows; **swarf** is a narrowing ribbon curling ahead of the point, one edge lit.

## 3. Colour logic

- The print is two values, paper and ink; all tone is line density.
- Colour is **transparent wash only**, in muted earth and mineral pigments, one stronger pigment at most. Never opaque, never on lettering, rules or paper outside the figure.
- Reserve it: the whole subject at one moment, or only the part that matters — or none.
- Example wash sets: an amber insect with blue-grey wings; a map with a sea-green coastal band on buff land; one madder-rose organ on an otherwise black anatomy plate.

## 4. Type & subtitles

- Lettering belongs to the plate: **roman capitals** (Bodoni Moda; title ~44–56 px, wide tracking; labels ~15–19 px), **italics** for scientific names (~20–24 px), **script** (Pinyon Script) for notes, fixed size, balanced over two lines, never shrunk.
- Roman letters are **cut glyph by glyph**; script is **written** in one left-to-right stroke. Nothing fades in.
- Subtitles: script on a deckled paper slip, bottom centre, ≤ 2 lines, never over a label. Hold ≥ max(1.8 s, speech + 0.6 s). An engraved note stays in frame chars ÷ 12 + 1 s from when it starts writing.

## 5. Motion quality

- **Cutting order is the animation**: outline → first hatching sweeping across each form → crossing → darks, hair, stipple. Strokes run at constant burin speed, many at once (a few for outlines, dozens for hatching).
- A long single stroke may be followed by the camera; start it partly cut so no frame is empty. Keep a full build to a few seconds.
- Roundels fly on an eased arc with a small lift, growing log-linearly to size. Colour blooms from one point with a ragged front and a wet rim that dries; regions staggered.
- Nothing fades or slides like UI: lines are cut, text cut or written, colour blooms, sheets are pressed, peeled or laid down.

## 6. Camera grammar

The camera is a **loupe over a sheet**. A vocabulary, not a route. Opening and ending come from the topic.

| Move | Expresses | Can serve |
|---|---|---|
| Loupe following the burin tip | One point of attention; making | a first mark; a signature |
| Log-zoom pull-out | The line was part of something larger | scale reveal; context |
| Push to a part, ride with its roundel | Where → what, in one take | an invisible detail; a mechanism |
| Tilt/pan along the sheet at reading zoom | Labels in order | a parts list; a coastline |
| Pull back while something flies | Everything placed in relation | acceleration; summary |
| Locked frame, or a ≤ 2 % breathing push | The plate as document | reading time; colour moving |
| Raking view across the copper | The groove as depth | the cost of craft |
| Cut from mirrored copper to true proof | Reversal | a hidden truth; before/after |

Framing: subject inside the plate mark, labels and roundels in the margins; order details so push-ins never crop a note early. Transitions from printmaking only (proof pulled, tissue guard laid over, region burnished out and re-cut, new sheet on the bed); no dissolves or wipes.

## 7. Sound palette

- **Foley by material**: paper (peel crackle, slip tapped down, tissue rustle, sheet whoosh); press (roller rumble, thump); copper and steel (high band-passed burin hiss with chatter and faint plate ring, swarf pings, a tick on lift, circular scribe, burnishing rub); ink and water (pen scratch, ticks for cut letters, a water plip and wet brush swish). Hatching = micro-scratches denser each pass.
- **Room**: a quiet workroom (faint clock), paper room once the print exists.
- **Instruments** (choose): harpsichord, string quartet, solo cello or viola da gamba, lute, chamber organ, glass harmonica for a cold subject. Plucked and dry while lines are cut; bowed or sustained only when something soft arrives; tiny tings for a scribed ring, a low pluck on landing.
- **Silence** is real: cut room tone too, keep at most one small sound.
- **Mix**: melody an octave above the voice, music ~half under speech, −14 LUFS. Voice: a quiet curator or naturalist.

## 8. Native moves

A menu: use the ones your story needs.

- **The cut.** Burin mid-stroke, swarf rising, nothing else. *Fits:* the first line of a treaty; a watchmaker's scribe; a coast being charted.
- **The three passes.** Form gains volume pass by pass. *Fits:* a building from its plan; a portrait emerging; a skill improving.
- **Magnification roundel.** Ring scribed, burnished, re-cut larger, flown to a margin with a leader, label cut on landing. *Fits:* a gear in a clock; a pollen grain; a harbour inset on a chart.
- **The proof.** Sheet peels off; mirrored copper becomes true paper. *Fits:* a secret out; a draft made final; a coin's die and strike.
- **States of the plate.** A region burnished out and re-cut. *Fits:* a border redrawn; before/after; a design revision.
- **Hand colouring.** Washes bloom after the print. *Fits:* one organ lit; a flag on a historical map; a ripening fruit.
- **Natural size.** A tiny true-scale figure beside the engraving. *Fits:* a seed by its tree; a chip by its circuit; a stamp by its enlargement.
- **The finished plate.** Every label and credit, locked. *Fits:* a museum label; a frontispiece; a certificate.

## 9. Pitfalls of the medium

- Uniform width reads as pen → swell hatches, pinch contours between runs (`hatch({swell})`, `outline({run, pinch})`), keep wMin hair-fine.
- Overlaps without occlusion → pass occluders as `excl` (subtracted ring by ring; even-odd would cancel overlaps).
- Outline-only parts beside a hatched body → hatch along each part's axis, a dark at every joint.
- Burin along the cut hides the groove; big skew looks like poking → ≤ 15°. Regular swarf helix reads as a spring → vary winding, twist, light one edge.
- Reflections over grooves wash them out → copper light first. Roundels authored small freeze sub-pixel → author large, scale in. Leaders hugging the subject read as crossing it → clearance.
- A long early stroke never draws → the ink's early exit must look ahead by the longest stroke.
- A push-in cropping a fresh note breaks the reading rule → put consecutive details on one side.
- Scientific names: TTS may manage, ASR won't → give the checker a plain spelling.

## 10. Engine

`demo/engine/`: `burin.js` (`B.Ink` ordered stroke store + `schedule`, `B.hatch`, `B.engraveTone`, `B.contourHatch`, `B.outline`/`B.stroke`, `B.stipple`, `B.fur`, tone fields), `plate.js` (`drawSheet`, `engraveText`, `writeScript`, `roundelFrame`), `wash.js` (`Wash`), `copper.js` (copper, burin, swarf), `index.js` (`engraveShape(svgPath, {at, light, spacing, style})`: any SVG shape → engraved figure). `demo/example/index.html` engraves and colours a four-pointed spark in ~20 lines; code and function table in DEMO.md "Engine reference".

## 11. Variation space

You decide subject, details, order, opening, ending, camera path, colour, pacing and music. Use cases are **grammar for the order and duration of information**; build your own timeline from the user's facts.

| Use case | Information order | Hold per layer | Length |
|---|---|---|---|
| **Museum label / case screen** | title + scientific name → detail + term + note (×N) → where to see it | title ≥ 2.2 s; note ≥ chars/12 + 1 s; final ≥ 4 s | 30–40 s |
| **"One minute on …"** | question → name → 2–3 facts → one number → follow prompt | number ≥ 2.5 s alone | 35–60 s |
| **Textbook figure** | figure → parts labelled one by one → caption | label ≥ chars/12 + 1 s | 20–45 s |
| **Craft heritage** | object → 2–3 craft details → maker / edition | as above | 30–45 s |
| **Map / site plan** | place → insets → legend → visiting info | inset ≥ 3 s; legend ≥ 4 s | 30–45 s |

All far from our demo:

- Structures: **states of one plate** (one view re-cut three times as a place changes); **a book of plates** (four small plates turned like pages, one fact each, no roundels); **a dissection** (parts labelled in teaching order, colour only on the part taught).
- Openings: **the finished proof burnished back** to its first line; **on paper at 1×** (title cut first, figure grows below); **raking light over blank copper** as the design is traced.
- Endings: **plate beside its proof**; **the natural-size figure** held alone; **a blank new sheet** laid on the stack.

Swapping `demo/content.json` and rebuilding is a technical check that the engine re-flows, not a way to make a film.

---

How our demo was made (story, shots, score, end card, build, content fields): [DEMO.md](DEMO.md). Read it after your treatment exists.