Object

Incandescent lamp

A wire heated until it glows — and the object that created the tungsten industry, then made itself illegal.

An incandescent lamp passes current through a filament until it is hot enough to emit visible light. The physics sets the problem: useful light needs temperatures around 2,500 °C, and almost nothing survives that. Carbon filaments evaporated and blackened the glass; the answer was tungsten, which has the highest melting point of any metal at 3,422 °C.

Almost all of the energy leaves as heat rather than light, which is inherent rather than a design failure — a hot object radiates mostly in the infrared, and no amount of engineering moves that. It is why the lamp was legislated out of existence rather than improved.

History

Many independent inventors from the 1840s; Edison's and Swan's commercially viable carbon-filament lamps date from 1879 and 1878. The material story that matters comes later: William Coolidge's ductile tungsten process at General Electric in 1906 to 1910 made a drawable tungsten wire possible, and tungsten filaments have been standard since.

Irving Langmuir's work through the 1910s added the two refinements still in use — a coiled filament, which reduces heat loss to the fill gas, and an inert gas fill instead of vacuum, which suppresses evaporation. The halogen lamp of 1959 adds a regenerative cycle that returns evaporated tungsten to the filament.

Phase-outs began in the 2000s and are now near-universal for general lighting.

Cultural significance

It is the object by which electricity entered ordinary life, and the reason electrical distribution networks were built at all — lighting was the application that justified the grid, and everything else followed the wires.

It is also the standing example of the Phoebus cartel, which from 1925 fixed lamp lifetimes at 1,000 hours by agreement, and is the best-documented case of deliberately limiting a product's life. That the physics genuinely does trade lifetime against efficiency is what makes the case interesting rather than simple.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is made of

Tungsten — element · the filament, and the reason the metal has an industry — nothing else stays solid at the temperature useful light requires
Soda-lime glass — material · the envelope, which has to seal against metal without cracking as both expand
Argon — element · the fill gas, which suppresses evaporation from the filament and is why a modern lamp is not a vacuum

is used as

Lighting — application · and almost all of the energy leaves as heat, which is inherent rather than a design failure and is why it was legislated away

was succeeded by

Phosphor — material · by way of fluorescent and then LED lighting, where the light comes from a phosphor converting shorter wavelengths rather than from anything being hot

Sources

Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)
Material World
Our own writing

Questions this page answers

Where it comes from, and what it becomes

Follow Incandescent lamp back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Incandescent lamp → is made of (the filament, and the reason the metal has an industry — nothing else stays solid at the temperature useful light requires) → Tungsten → is produced by (reduced from the oxide, at a temperature few other metals demand) → Smelting → takes as input (as the element removed, not added) → Oxygen → is produced by (the largest output by tonnage, and the reason air separation units sit beside steelworks) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
Incandescent lamp → is made of (the envelope, which has to seal against metal without cracking as both expand) → Soda-lime glass → is produced by (drawn off the tin bath as a sheet flat on both surfaces) → Float glass process → takes as input (with difficulty, which is why flat borosilicate costs several times what window glass does) → Borosilicate glass → is produced by (with boron oxide replacing most of the soda, which is what drops the thermal expansion to a third and lets a hot dish go into water) → Glass melting → takes as input (as the stabiliser, and without it a soda-silica glass would slowly dissolve in water) → Limestone
Incandescent lamp → is made of (the fill gas, which suppresses evaporation from the filament and is why a modern lamp is not a vacuum) → Argon → is produced by (drawn from an intermediate height in the column, between nitrogen and oxygen) → Air separation → takes as input (the feedstock, and an unusual one in being free, unlimited and available anywhere — the cost is entirely the energy to liquefy it) → Air
Incandescent lamp → is made of (the envelope, which has to seal against metal without cracking as both expand) → Soda-lime glass → is composed of (as silica sand, the principal former) → Quartz
Incandescent lamp → is made of (the envelope, which has to seal against metal without cracking as both expand) → Soda-lime glass → is produced by (drawn off the tin bath as a sheet flat on both surfaces) → Float glass process → takes as input (the batch is essentially sand, with soda ash to lower the melting point and limestone to stop the result dissolving in water) → Sand → is sourced from (the ultimate source of most of it — granite weathers, the feldspar becomes clay and washes out, and the quartz survives as grains) → Granite → is composed of (by volume, alongside feldspar and lesser mica) → Quartz
Incandescent lamp → is made of (the filament, and the reason the metal has an industry — nothing else stays solid at the temperature useful light requires) → Tungsten → is produced by (reduced from the oxide, at a temperature few other metals demand) → Smelting → takes as input (roasted to drive off sulfur, then reduced to copper) → Chalcopyrite

These are the most distinct paths back. Incandescent lamp can be traced through others besides.

Downstream — what it becomes

Incandescent lamp → is used as (and almost all of the energy leaves as heat, which is inherent rather than a design failure and is why it was legislated away) → Lighting