Gustaf Dalén – Beacon lighting

Gustaf Dalén registered a total of 99 patents during his lifetime. He invented revolutionary systems for beacon lighting, founded Swedish industrial gas company AGA and continued to work even after a serious accident left him blind. He was awarded the Nobel Prize in Physics in 1912.

Childhood and early signs of innovative spirit

Nils Gustaf Dalén was born in 1869 in Stenstorp in Västra Götaland County, Sweden. His parents, Anders Johansson and Lovisa Dahlén Johansson, were affluent farmers. Gustaf´s four siblings also achieved a level of repute in their respective fields. Gustaf loved to invent things. One of the most famous stories from his childhood concerns the alarm clock he invented when he was 13 years old. Gustaf liked to have his coffee first thing in the morning. With this in mind, he rigged up an old wall clock his father had given him with a bit of sheet metal, a striking mechanism and a cylinder covered in sandpaper. Fifteen minutes before the clock was supposed to strike, the cylinder would begin to spin and strike a match. The match hung over a gas oil lamp and over the lamp was a kettle of coffee. When Gustaf´s alarm clock went off, the young inventor woke in a lighted room with a pot of hot coffee waiting for him.

Meeting Gustaf de Laval

As an adult, Gustaf worked as a gardener and ran a dairy, and became more and more interested in technology and engineering as time went on. It wasn´t long before he invented a device that could determine the fat content of milk. He took his invention to Stockholm to meet the renowned inventor, Gustaf de Laval. It turned out that de Laval had just been awarded his own patent for a similar device. De Laval advised the disappointed Gustaf Dalén to further his education. Dalén took this advice and entered Chalmers University of Technology in Gothenburg in the autumn of 1892. Four years later, he went to Switzerland to study at Eidgenössisches Polytechnikum in Zurich, one of the foremost technical universities of that time.

Dalén’s first successes

Upon his return to Sweden, Gustaf was made chief engineer at Svenska Karbid- och Acetylen AB, a company that later developed into the world renowned company AGA, established in 1904. Gustaf was very interested in acetylene, a highly luminous gas used extensively at the end of the 19th century. Acetylen was considered promising as a fuel for lighthouse beacons. The problem was that such beacons demanded considerable monitoring and a great deal of gas. Gustaf´s first assignment — and his breakthrough — was to find the solution.

Dalen Flasher

Gustaf´s revolving light apparatus dispersed the gas into bubbles that were ignited by a perpetual flame. This made the beacons emit a flashing light and conserved almost 90 percent of the gas. The distance between the bubbles could also be varied so that observers could differentiate between beacons according to how quickly or slowly they flashed.

Sun valve

Gustaf thought it was unnecessary for the beacons to flash even during the day. This led him to develop one of his most famous inventions, the sun valve, which he completed in 1907. The principles were very simple: a dark object attracts more sunlight than a light object, and heat causes dark objects to expand. The sun valve contained one black rod surrounded by three shiny rods. The black rod was connected to a membrane that opened and closed the flow of gas. When the sunlight expanded the rod by two thousandth of a millimetre, the beacon was extinguished. When night came, the rod retracted and the gas was once again released to the perpetual flame, causing the beacon to begin flashing again. “It won´t work,” Thomas Edison is rumoured to have said about the sun valve. But it did work. In 1912, AGA received a prestigious order — all of the beacons in the Panama Canal. When the Blockhusudden beacon in Stockholm, the first sun valve beacon in the world, was electrified in 1980, it was discovered that the sun valve had never needed to be repaired!


To minimize the risks associated with the explosive acetylene gas, Gustaf developed a silicon-based porous substrate consisting of substances such as cement, coal and asbestos. This compound was able to absorb the acetylene so that the gas could be transported.

Dalén Mixer

The Dalén Mixer gave lighthouses greater luminosity. Acetylene and oxygen were mixed in specific proportions and then used to ignite an incandescent mantle, which in turn was connected to a system of lenses that reflected the light.
These four inventions lay the foundation for AGA´s subsequent success.

The accident

On 27 September 1912, Gustaf suffered a horrible accident. He was experimenting with heated gas bottles to see how much pressure they could sustain. A bottle exploded and he was severely injured. He survived, but lost his sight.

Nobel Prize

A few weeks after his accident, Gustaf was notified that he had been awarded the Nobel Prize in Physics “for his invention of automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys.”

Willpower and optimism

His blindness was difficult to accept, but in 1913, Gustaf returned to AGA and led the company for another twenty-five years. His innovative spirit was unshakable and in the 1920s, he developed a new fuel-efficient stove and oven unit, the AGA Cooker, which became a household name across the globe.

Gustaf Dalén succumbed to cancer in 1937.


Peter Du Rietz

Peter Du Rietz


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Last updated 7 December 2021.