BiscuitClear

How are biscuits made?
A biscuit is bread's opposite. Fat coats the flour so the dough breaks instead of stretching, a pinch of powder turns to gas in the heat, and a steel band carries it through sixty metres of oven until only 2% of it is water. Take one apart, run the oven yourself, and find out why it goes soft in the monsoon and breaks in your chai.

▶ Play with it  ·  Read the 60-second explainer  ·  Watch the 40-second video

In 60 seconds

1. Flour, fat, sugar and almost no water. A biscuit is flour, fat and sugar with a little water and a pinch of leavener. Bread leaves the oven about 38% water. A biscuit leaves at about 2%, which is why it snaps and why a sealed packet keeps for months. The word means twice baked.
2. Short dough: the opposite of bread. Wet, kneaded flour builds a stretchy gluten net, which bread needs. A biscuit dough avoids it: fat coats the flour particles, little water goes in, sugar takes its share of that water, and mixing is brief. The dough breaks instead of stretching, which is why baking fat is called shortening.
3. Gas without yeast. Baking soda gives carbon dioxide when heated, and twice as much when it meets an acid. Factory biscuits also use ammonium bicarbonate, which turns entirely into gas above about 60 °C and leaves nothing behind. The gas swells tiny air cells beaten in during mixing. Steam does even more: one gram of water makes about 1.7 litres.
4. Rolled, moulded or cut by a wire. A hard dough such as Marie is rolled thin, cut by a spinning cutter and pricked with docker holes so steam can escape and it bakes flat. A crumbly short dough, like a glucose biscuit's, is pressed into moulds engraved on a roll, with the name cut in mirror writing. Soft cookie dough is sliced by a wire.
5. The oven that never stops. A steel band carries the pieces through a tunnel oven 60 metres or more long. The first zone lets them rise, the middle one boils off the water while the biscuit sits near 100 °C, and the last one browns the dry surface. Baking time is simply band speed: about five minutes.
6. Crisp, soft, dunked. Water moves from high water activity to low. A fresh biscuit is near 0.1, drier than almost any air, so in monsoon humidity it soaks up water and loses its snap, while a cake at 0.9 dries out. In chai, tea is pulled into the pores by capillary action, and once it is wet right through, it breaks.

Words worth knowing

Term	Meaning
Baker's percent	A recipe written as parts by weight for every 100 parts of flour.
Gluten	The stretchy network formed when wheat proteins are wetted and worked. Bread needs it, and biscuits keep it short.
Shortening	Baking fat. It coats flour particles so less gluten forms and the bite is tender and crumbly.
Chemical leavener	A powder that makes gas in the dough: baking soda, baking powder or ammonium bicarbonate.
Docker holes	Holes pricked through a dough piece so steam can escape and the biscuit bakes flat instead of blistering.
Rotary moulder	A machine that presses short dough into moulds engraved on a roll, then pulls the shaped pieces out onto a belt.
Tunnel oven	A long oven that a moving steel band carries biscuits through, in zones of different temperature.
Maillard reaction	Sugars and proteins reacting in a hot, dry surface to give brown colour and baked flavour.
Water activity	How freely the water in a food can leave, from 0 to 1. Water moves from the higher value to the lower.

A short history

From bread baked twice for soldiers and sailors to the glucose biscuit dunked in chai across India.

• 1677 · A pound of biscuit a day (Samuel Pepys, The Admiralty, London)
• 1790 · Nankhatai from a Dutch bakery in Surat (Faramji Pestonji Dotivala (as told by the Dotivala family), Surat, Gujarat)
• 1796 · A powder that makes dough rise (Amelia Simmons, Hartford, Connecticut)
• 1829 · Steam makes the navy's biscuit (Thomas Tassell Grant, Royal Clarence Victualling Yard, Gosport)
• 1846 · Machinery that never stops (George Palmer and Thomas Huntley, with the ironfounder William Exall, King's Road, Reading)
• 1892 · Britannia starts with Rs 295 (A group of British businessmen; later the Gupta brothers and C. H. Holmes, Calcutta (Kolkata))
• 1924 · The steel band oven and the rotary moulder (A Dutch machinery maker, then Baker Perkins, Britain)
• 1939 · Parle Gluco (Parle Products, Vile Parle, Bombay (Mumbai))

The full story, with 28 moments, charts, people and 49 sources: glassbox.how/e/biscuitclear/history. The data lives in history.json.

Video and slides

Made with the Glassbox studio from this box's storyboard (window.glassbox.director). Free to reuse under CC BY 4.0.

File	What	Size
glassbox/reel.mp4	Reel / Short, with captions and soundtrack	1080×1920
glassbox/video.mp4	YouTube video, with captions and soundtrack	1920×1080
glassbox/slide-1…10.jpg	Instagram carousel	1080×1350
glassbox/thumb.jpg	YouTube thumbnail	1280×720
glassbox/cover.jpg	Share card and repo social preview	1200×630
glassbox/history-reel.mp4	“History in 10 moments” Reel / Short	1080×1920
glassbox/history-slide-*.jpg	History carousel	1080×1350
glassbox/post.json	Post copy and schedule used by the publish kit

Privacy

This box has no accounts and no ads, and it ships its own fonts and libraries. When you run it yourself it sends nothing anywhere. On glassbox.how, the site's /bar.js also loads Glassbox's analytics: Google Analytics to count visits (it asks first in the EU, UK and Switzerland, and stays off when your browser sends Global Privacy Control or Do Not Track) and ClickTrust to detect bots.

It remembers a few things in your own browser only, and never sends them anywhere:

Browser storage key	What it holds
biscuitclear.v1	Which chapters you have opened, your best quiz scores, and sound on or off.

Exactly what each one sees is at glassbox.how/privacy.

Licences

• Code: MIT. Use it, change it, ship it.
• Explanations, text, images and videos (glassbox.json, glassbox/): CC BY 4.0. Credit “Glassbox, glassbox.how/e/biscuitclear”.
• Third-party parts keep their own licences: three.js (MIT), Geist, Instrument Serif (SIL OFL 1.1).
• The Glassbox name and logo aren't covered by either licence. See the terms.

Found a mistake? Open an issue. Corrections happen in public.

Run it

It's plain HTML, CSS and JavaScript. No build step and no dependencies. Run locally, it contacts no other website.

python3 -m http.server 8000

Three.js and the fonts ship in vendor/ and fonts/, so it also works offline.

Then open http://localhost:8000.

How it's built

File	What
index.html, css/app.css	The page and its styles
js/app.js, js/stage.js, js/ui.js, js/kit.js	The shared Glassbox 3D engine: chapters, 3D stage, controls, quiz, video director
js/chapters/*.js	One file per chapter: the 3D model, controls, text, key terms, quiz and video scenes
js/physics.js	The numbers and models, with their sources: typical recipes, the gluten index, leavening gas, the tunnel oven bake, water activity and dunking. No 3D, so it runs in Node
js/biscuit.js	Shared parts: chart boards, the screen layout, instanced particles, the microscope frame and the 3D biscuits
glassbox.json	Title, question, explainer beats, key terms, browser storage and credits shown on glassbox.how
reel in each chapter	The storyboard the Glassbox studio records into short videos
glassbox/	The published video, slides, thumbnail and post copy
fonts/, vendor/three/	Self-hosted Geist and Instrument Serif (SIL OFL 1.1) and three.js (MIT)