AgarbattiClear

How does an agarbatti work?
An agarbatti never burns its perfume. A tiny ember at about 650 °C creeps down the stick at 3 mm a minute and boils the scent out of the paste just ahead of it. Blow on the tip, follow the smoke from a smooth thread into curls, and see what one stick does to the air of a closed room, and what an open window undoes.

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

In 60 seconds

1. A splint, a paste and an ember. An agarbatti is a bamboo splint with about a millimetre of dried paste round it: charcoal and wood powder as fuel, sticky jigat bark as binder, and a fragrance, either ground into the paste (a masala stick) or soaked in afterwards (a dipped stick). A common Indian stick is about 3 mm thick, 20 cm long and under 2 grams. Dhoop is the same paste with no bamboo, and a cone is dhoop in another shape.
2. It smoulders: no flame. Oxygen reacts on the hot surface of the char, which glows at about 610 to 640 °C on measured Indian sticks. The ember is a heat balance: heat made must equal heat lost as glow and to the air, plus heat that soaks back to dry and char the next slice. That is why the front creeps at about 3 mm a minute, why blowing brightens it, why a thick stick is slower and why a damp one goes out. A few millimetres ahead of the ember the stick is at 100 to 300 °C, hot enough to boil the fragrance out without burning it.
3. A thread, then curls. Hot air above the ember rises as a smooth laminar thread, then breaks into turbulent curls a hand's width or two up, sooner in a draught. The smoke is a mist of particles mostly 0.06 to 2.5 micrometres across, with carbon monoxide and organic vapours. Scent crosses a room in about a minute because the air drifts and carries it; diffusion alone would take days. A backflow cone's smoke pours downward because, once cooled, it is denser than air.
4. In the room: open a window. Lab tests found 5 to 56 mg of PM2.5 for each gram of incense burnt. One stick in a shut 30 m³ room can lift fine dust into the hundreds of micrograms per cubic metre; the WHO guideline for a day's average is 15 and India's standard is 60. Going from a shut room to wide-open windows cuts what a stick adds to roughly a tenth. Long-term daily use has been linked in a large Singapore study to more airway cancers of one kind and more heart deaths: associations, not proof. Fewer sticks, shorter time and fresh air are the practical answer.
5. Rolled, dried, dipped, packed. The dough is rolled round each splint by hand on a wooden board, or extruded round it by machine: about 80 kg a day from one automatic machine. Sticks dry in the sun in great fans, quickly on a dry day and very slowly in the monsoon, because evaporation depends on the gap between the wet surface and the air. Mysore Agarbathi has been a registered Geographical Indication since 2005, and the Bureau of Indian Standards released its agarbatti standard, IS 19412, in December 2025.
6. One idea, many shapes. Dhoop and cones, resins such as loban, sambrani and guggul dropped on a glowing coal, thin coreless Japanese koh, Chinese joss sticks and hanging coils, Tibetan rope incense, Arabian bakhoor and church frankincense are all ways of warming fragrant matter until it leaves as scent and smoke. Because an ember creeps at a steady speed, a stick also measures time: incense clocks were used in China from about the 6th century.

Words worth knowing

Term	Meaning
Agarbatti	An incense stick: scented paste rolled or extruded round a bamboo splint.
Smouldering	Slow, flameless burning on the surface of a solid, seen as a glow.
Heat balance	The ember stays alight only while the heat it makes equals the heat it loses plus the heat it passes to the next slice.
Pyrolysis	Breaking a material down with heat alone, turning wood into char, vapours and tars.
Jigat	Powdered bark of Litsea glutinosa and related trees, which turns sticky with water and binds the paste.
Laminar and turbulent flow	Smooth, orderly flow, and flow broken into swirls. Incense smoke shows the change from one to the other.
PM2.5	Particles finer than 2.5 micrometres, measured in micrograms per cubic metre of air. Incense smoke is nearly all PM2.5.
Air changes per hour	How many room-fulls of fresh air replace the old air each hour: about 0.3 with everything shut, 5 or more with windows wide open.
Dhoop	Incense with no bamboo core: a solid stick, log or cone. Also the old Sanskrit word for incense offered in worship.

A short history

5,000 years from resin on hot coals to a bamboo stick with a BIS standard.

• 3100 BCE · One of the oldest incense burners (Craftspeople of the A-Group culture, Qustul, Lower Nubia)
• 1000 BCE · Dhupa in the Vedas (Vedic poets and priests, Northern India)
• 200 BCE · The incense road at its height (Caravan traders of South Arabia and the Nabataeans, Dhofar and Shabwa to the Mediterranean)
• 540 · Telling the time with incense (Buddhist monks and scholars, China)
• 1895 · The bamboo-core agarbatti takes over in India (Stick makers of the Mysore region, Mysuru and Bengaluru, Karnataka)
• 2002 · The smoke is measured (J. J. Jetter, Z. Guo, J. A. McBrian and M. R. Flynn, US Environmental Protection Agency, North Carolina)
• 2005 · Mysore Agarbathi becomes a Geographical Indication (All India Agarbathi Manufacturers Association, Chennai (GI Registry) and Karnataka)
• 2008 · A long study of daily use and cancer (Jeppe Friborg, Jian-Min Yuan, Woon-Puay Koh, Mimi Yu and colleagues, Singapore)

The full story, with 32 moments, charts, people and 32 sources: glassbox.how/e/agarbatticlear/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
agarbatticlear.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/agarbatticlear”.
• 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/smoulder.js	The physics, with its sources: the ember's heat balance, the temperature ahead of it, the plume, the room model and drying
js/agarbatti.js	Shared 3D parts and chart boards: the stick, its stand, particles and the layout rules
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)