Printing and Movable Type

Difficulty: moderate for woodblock printing; high for a durable movable-metal-type shop, where several crafts must work to compatible dimensions. Prerequisites: A woodblock shop needs a printable sheet material such as paper, seasoned carving wood, relief-printing ink, carving tools, and a rubbing pad or simple press. Movable metal type additionally needs oil-based ink, metal casting, woodworking for the press and furniture, and steel for punches. Punchcutting, matrix making, type founding, composing, and presswork are distinct skilled trades.

Why it matters

Of the things in this repository that you have to build, this has the longest reach — see the ranking in the README for how it sits against the things that need no building at all. It isn't close.

Everything else here makes a thing. Printing makes it much cheaper to preserve and circulate knowledge that does not die with one person. One locked forme can produce hundreds of substantially repeatable copies, so readers can cite the same edition and page. Copies are not automatically identical or correct: composition errors, uneven inking, type wear, paper variation, and corrections made partway through a run all create differences. Edition identification, proofing, collation, and retained reference copies are what make repeatable text dependable.

European print production expanded rapidly after the mid-15th century. Cheap, repeatable editions helped ideas travel through religious reform, scholarship, administration, and education, but the press did not by itself cause the Reformation, modern science, or mass literacy. Schools, readers, vernacular languages, patronage, censorship, transport, and paper supply all shaped those outcomes.

Why Gutenberg's version won

Printing existed long before him. Chinese woodblock printing dates to at least the 7th century, and Bi Sheng made movable ceramic type around 1040; Korea cast metal movable type by 1234 and printed the Jikji in 1377, decades before Gutenberg.

What Gutenberg assembled around 1450 was a system where every part was solved at once:

1. The adjustable type mould — casting many interchangeable, dimensionally consistent pieces of type quickly. This is a central enabling component.
2. A type metal alloy that melts low, casts sharp, and is hard enough to survive the press.
3. Oil-based ink that sticks to metal type instead of beading off.
4. A screw press adapted from wine and paper making.
5. Paper, cheap and available.

Miss any one and this particular metal-type system becomes impractical. Note that alphabetic writing makes movable type far more attractive — a Latin fount needs a few hundred sorts, while Chinese needs tens of thousands, which is a large part of why woodblock remained more practical in East Asia.

The five crafts

1. Punchcutting

For each character, a master craftsman cuts the shape in relief on the end of a hardened steel punch, working at actual size — often only 2–3 mm tall — with files, gravers, and a magnifier (see optics, and note this is a genuine use case for spectacles).

Cut the punch in soft annealed steel, then harden and temper it (see iron and steel) so it can be struck into copper without deforming.

This is the most skilled job in the trade. A full fount is 150+ punches including capitals, lowercase, numerals, punctuation, and ligatures, and each must look like it belongs to the same family. Budget months.

2. Striking the matrix

Drive the hardened punch into a small block of copper with a hammer. This leaves a sunken (intaglio) impression — the matrix. Then "justify" it: carefully file and dress the matrix so the character sits at exactly the right depth and is square and centered relative to the block.

Copper is chosen because it's soft enough to take the strike cleanly but tough enough to survive thousands of casts.

3. The type mould — the actual invention

This is the piece worth understanding properly.

The mould is a two-part hand-held jig, lined with wood so you can hold it while it's hot, that clamps around the matrix at its base. Its critical property: it is adjustable in width but fixed in height and depth.

Why that matters: every letter must be exactly the same height-to-paper (so all letters print with equal pressure) and exactly the same body depth (so lines lock up square) — but an i must be narrow and an m must be wide. The adjustable mould delivers all three constraints at once from a single tool.

Casting: clamp the matrix in, pour molten type metal in with a small ladle with a flick of the wrist to drive metal into the fine detail, wait a moment, spring the mould open, and eject the type. An experienced caster produces several thousand sorts a day. Break off the sprue (the "jet"), rub the sides smooth, and sort into cases.

4. Type metal

Lead alone is too soft and shrinks as it solidifies, so letters come out rounded and weak. The traditional alloy is roughly:

Antimony is the clever part. Almost all metals shrink as they freeze; antimony expands, so the alloy holds its dimensions and pushes into every fine detail of the matrix. Without it you cannot cast sharp small type.

Antimony commonly occurs in stibnite, but roasting or reducing an unknown ore can release toxic antimony, sulfur, arsenic, mercury, or lead compounds. Obtain an identified, analyzed metal or alloy from a controlled metallurgical process; this guide does not supply a safe extraction specification.

The alloy melts around 250–300°C — easily reachable, and far below the point where your matrices are at risk.

Lead hazard. Type founding involves molten lead and lead dust, and compositors handled type all day. Read the warnings in silver: lead can accumulate and cause permanent harm. Outdoor location alone is not exposure control. Use a contained process with effective source-capture exhaust, exposure monitoring, temperature control, compatible protective equipment, hygiene/change facilities, and controlled dross and waste. Keep food, drink, children, and unprotected people out of the foundry. Antimony and its fume are also toxic; if these controls and competent supervision are unavailable, do not found type metal.

5. The press

A screw press adapted from wine and paper presses (see woodworking):

• A heavy timber frame braced against the ceiling and floor so it doesn't rack.
• A large wooden screw driven by a lever bar, pressing down a flat platen.
• A sliding carriage carrying the type forme, run in and out under the platen on rails.
• A hinged tympan (a padded frame the paper is laid on) and frisket (a paper mask that shields the margins from ink).
• Points — small pins that pierce the sheet, so when it's turned over to print the second side it registers in exactly the same position. Registration is what makes double-sided printing possible.

The platen must strike flat and parallel with a short, evenly distributed pressure. On a common wooden press the platen was often only large enough for half a full-sheet forme, so printing one side of one sheet took two bar pulls: move the first half under the platen and pull, advance the bed, then pull the second half. Turning the dry sheet and printing its reverse was a separate pass from a second forme, again usually requiring two pulls.

Setting and printing

1. Prepare and identify the copy. Establish one legible, approved master copy; mark headings, paragraphs, illustrations, tables, and any unusual spellings. Assign the work an edition statement, date, printer/publisher, place, and a short imprint or job number. Number the copy leaves and preserve this master so later corrections can be checked against a stable source.
2. Compose. The compositor picks sorts from a divided case, letter by letter, into a hand-held composing stick set to the line width, reading upside down and backwards. (The familiar terms uppercase and lowercase come from literally which case the capitals sat in.)
3. Justify each line by inserting blank spaces of varying thickness until the line is exactly full and tight. A loose line falls apart when lifted.
4. Assemble lines into a page on a galley, then arrange pages in the correct scrambled order on the imposing stone so that they come out sequential when the printed sheet is folded. Working out that imposition scheme is a genuine puzzle and getting it wrong wastes a whole run.
5. Proof and correct. Pull a proof before the production run. A corrector checks it against the approved master; for dense work, a copyholder reads the master aloud while a second person follows the proof. Mark every correction, unlock and replace the wrong sorts, then pull another proof. Check running heads, folios, signatures, tables, cross-references, and imposition as well as spelling. Keep the approved proof and correction log with the edition record.
6. Lock up the corrected forme in an iron frame (chase) using tapered wooden or metal wedges (quoins). Test by lifting the whole forme — if any type falls out, it isn't tight.
7. Ink with leather ink balls (a stuffed leather pad on a handle), rolling and dabbing to get an even film. Too much ink blots and fills the counters of letters; too little gives grey patchy text. Later, a composition roller of glue and molasses does it far better and faster.
8. Print and inspect: lay a slightly damp sheet on the tympan, fold down the frisket, run the carriage under the platen, make the pulls needed for the whole forme, release, slide out, and peel off. Compare samples throughout the run with the approved proof. If a correction is made after production starts, record the stop-press change and keep the earlier and later sheets separate; they are variants, not identical copies.
9. Complete and collate. Hang sheets to dry, print the reverse from its forme, then fold and gather by signature. A collator checks every gathering against the approved master or reference set before sewing and binding. Preserve at least one complete reference copy with its imprint, edition record, sheet count, and correction log. Errors found too late for economical correction belong in a clearly identified errata slip or list.

Output units matter: a pull is one operation of the bar. On a two-pull common press, two pulls produce one printed sheet-side. Smithsonian's survey reports that a two-person crew could produce up to about 240 sheets printed on one side per hour under good conditions. Printing the reverse later doubles the press work, so that rate is at most about 120 completed two-sided sheets per press-hour before allowing for proofing, make-ready, drying, turning, corrections, or forme changes. Record pulls or sheet-sides explicitly instead of calling all of them "impressions."

Ink — the part everyone underestimates

Water-based ink beads off metal type and prints nothing. You need an oil-based ink, which Gutenberg borrowed from oil painters:

1. Obtain a characterized printing varnish, or have linseed oil polymerized in a purpose-designed, temperature-controlled, indirectly heated system with ventilation and rated fire protection. An open pot outdoors is still a severe boil-over, vapor, and oil-fire hazard; see oils and fats.
2. Grind lampblack (soot from an oil lamp) into the varnish on a stone slab with a muller until utterly smooth and free of grit.
3. Add a little rosin for tack and body.

Aim for the consistency of stiff honey — it must cling to the type, transfer to the paper under pressure, and not spread. This ink is why 15th-century printing is still deep black today.

What to print first

Think carefully — the first press's output shapes what the technology is for.

1. Practical reference: agricultural calendars, weights and measures tables, medical and sanitation instructions (see medicine), and the guides in this repo.
2. Basic literacy primers paired with teaching. A press has limited reach where few people read; primers help only when they use an understood language and are accompanied by teachers, learner time, and reasons to practise.
3. Mathematical tables — multiplication, logarithms, trigonometry. See mathematics and record-keeping. Carefully checked printed tables can improve navigation, engineering, and accounting. Proof them independently: a single typesetting error otherwise propagates through every copy and every calculation that uses it.
4. Maps and charts, for which see engraving below.
5. Whatever pays the bills — indulgences and legal forms funded early European printing, and commercial job printing is what keeps a press alive between books.

The related processes

• Woodblock (relief) — carve away everything that isn't the image. Simple, needs no metal, prints alongside type in the same forme, and is ideal for illustrations and for scripts with too many characters for movable type. Start here if you want printing tomorrow.
• Copperplate engraving (intaglio) — cut lines into copper with a burin, fill with ink, wipe the surface clean, and press damp paper into the lines under great pressure with a roller press. Far finer detail than woodcut, which makes it the right technology for maps, anatomical plates, and technical illustration. Note it cannot be printed in the same pass as type — different press, separate operation.
• Etching — coat copper with wax, draw through it with a needle, and let acid (nitric — see saltpeter) bite the lines. Easier than engraving because you're drawing, not carving.
• Stereotyping — cast a solid plate from a mould of a whole set forme, so you can reprint later without keeping the type standing. Frees up your type, which is your most expensive asset.
• Lithography (1796) — draw with a greasy medium on a prepared, fine-grained porous limestone, chemically process the surface, keep non-image areas damp, and roll on a compatible greasy ink. In reliable production it needs selected stone, grinding and levelling, gum and controlled etching/desensitizing chemistry, careful water/ink balance, transfer skill, and a dedicated scraper or lithographic press. It can reproduce freely drawn marks, but it is not a "flat stone plus grease" shortcut.

Failure modes

Sources and limits

• Smithsonian National Museum of American History — Wooden Hand Presses explains the common press, its half-forme platen, and two-pull operation.
• Smithsonian National Museum of American History — Galley Proof and Hand Cylinder Presses describes a proof as a trial print used to check composition before production.
• Library of Congress — Before Control-P: The Printing Process documents proofing, imposition, two pulls per full forme, drying, and reverse-side production.
• Smithsonian National Museum of American History — Lithographic Presses notes that lithography required a distinct press and production workflow.
• The Metropolitan Museum of Art — Lithography in the Nineteenth Century gives the process's origin and material basis.
• Library of Congress — Martin Luther as Priest, Heretic and Outlaw shows how print accelerated the spread of Reformation texts without reducing the movement to a single technological cause.

Historical rates are upper-end shop figures, not promises. Actual throughput and quality depend on page size, forme area, crew skill, paper, press condition, proofing standards, and the amount of correction and make-ready required.

Era notes

Woodblock printing: China, 7th century. Movable ceramic type: Bi Sheng, ~1040. Cast metal movable type: Korea, by 1234. Gutenberg's integrated system: ~1450.

The materials — lead, antimony, tin, copper, linseed oil, a screw press — were all available to the Roman Empire. Rome could have had printing. What it lacked was cheap paper (papyrus and parchment are both far too expensive to print on in quantity) and the conceptual leap of the adjustable mould. If you arrive in a society that already has paper, the gap between where they are and a working press is measured in months of craft work, not centuries.

Your knowledge advantages: the adjustable type mould as a concept, oil-based ink, damp paper, registration points, controlled proof-and-correction workflow, and the strategic insight that printing useful primers and checked tables early can compound when teachers, readers, and distribution also exist.