Necessity is indeed the mother of invention. In Axel Eriksson's case, it was the enormous energy shortage in Sweden in 1922 after the First World War. The government had announced tough savings measures. For this reason, it also increased the requirements for housing construction: From now on, better insulation was to be used in order to keep the heat in the house longer.

At the time, Dr. Johan Axel Eriksson, a Swede just in his early 30s, was teaching as an assistant professor of building techniques at the Royal Institute of Technology in Stockholm. He was conducting research on a large number of different aerated concrete samples. Because he knew: Blocks made of this material would not only be ideal for building faster than before. They would also insulate interiors much better than wood, which was a much-used building material at the time.

Eriksson accelerated the curing process of the porous mass of burnt shale limestone, water and aluminum powder by placing the sample in the laboratory autoclave. The porous mass survived the overnight autoclaving, and the resulting cured brick possessed greatly increased strength and a new, stronger crystalline composition. In the heat and pressure of steam curing, the silica and lime components had fused into a form of calcium silicate hydrate crystal, similar to the volcanic rock known in nature as tobermorite. The architect patented his invention in 1924 - and in Carl August Carlén found the merchant who could also bring the new building material to customers. First in Sweden, then all over the world.

Johan Axel Eriksson (1888–1961) and Carl August Carlén (1876–1960)

Carl August Carlén: From farm boy to industrialist

The future business partner had learned from scratch how to implement a good idea with patience. That's how the Swede Carl August Carlén made it from farm boy to successful industrialist.

Born 1876 as a son of a carpenter little Carl August lived with six siblings on a farm far south of Stockholm. Right after elementary school, Carlén went to agricultural school. In 1896, he found his first job as a storekeeper and barn bookkeeper. In 1903 he moved to Yxhults Stenhuggeri AB, a limestone quarry with a stonemasonry business near the town of Yxhult.

But Carlén fell out with the boss, left the company and returned in 1910 after a request from the board to take over the position as manager. In 1924, at the age of 48, he finally took over complete financial control and expanded the Swedish company into what would later become the global Ytong Group.

1924 was also the year in which the merchant became aware of autoclaved aerated concrete by Swedish architect Axel Eriksson. Carlén firmly believed that the new building material would become established. It combined many of the advantages of wood, but was easier and faster to process.

Carlén recognized the potential and secured the manufacturing license against the wishes of his supervisory board. A year later, the entrepreneur launched the first steam-cured aerated concrete. The beginning of a success story.

The former farm boy remained chairman of the board of the Ytong parent company until he was 80 years old. He died in 1960. His portrait still hangs in the Xella Group headquarters in Duisburg.

By the way: Why are the Ytong blocks packed in sunshine yellow? Here, too, there is a connection to Carl August Carlén: Because yellow roses were the favorite flowers of his wife Gerda. The man listened to his wife and packed the new building material in highly visible yellow.