Carl Johan Cronstedt

Carl Johan Cronstedt (25 April 1709 – 9 November 1779) was a Swedish architect, inventor, count, noble, civil servant, scientist and bibliophile.

Cronstedt was the son of Jakob Cronstedt (Olderman) and Margareta Beata Grundel. He was born in 1709 in Stockholm, Sweden. He married Countess Eva Margareta Lagerberg in 1744.

Cronstedt became a pupil of Christopher Polhem in 1729 and in 1733 was his apprentice. He studied civil engineering under Carl Hårleman and in 1743 became his successor as superintendent, a post he held to 1767. He carried out work at the following:

• Drottningholm Palace in the 1740s following Hårleman's architectial drawings.

• Maria Magdalena Church restoration in Stockholm after the 1759 fire.

• Construction of the new Amiralitetskyrkan in Karlskrona in 1760.

• Involved in the construction of Drottningholmsteatern 1764 to 1765.

• various town plans and park designs, including the town plan for Kasko in 1765.

• drawings for Saint Olai Church in Liverpool, which opened in 1767.

• 1739 - Member of the Royal Swedish Academy of Sciences, which was founded the same year.
• 1752 - Member of Swedish House of Lords.
• 1767 - President in Kammarrevisionen.
• 1769 - President in Kammarkollegium.

In the mid-eighteenth century Cronstedt, working together with Fabian Wrede, increased the efficiency of the wood-burning stoveroughly eightfold with a new technology and invention. Their 1767 redesign of the traditional wood-burning stove directed the smoke and heated gases through long flues that wound up and down inside the stove.The stove and its flues were built of special masonry bricks that captured, and then radiated, more heat from the burning process. The new technology changed the pattern designs of large interior building space for residences and other public buildings. It allowed more rooms to be heated with the same amount of firewood. It had significant social and economical consequences throughout Sweden and later throughout Europe and America up into the twentieth century. Cronstedt's invention had significant environmental significance as well because it saved forests from excess usage.

Cronstedt showed how in a ceramic wood-burning stove much more heat could be captured through a heavily tiled system of five long internal flues. The innovation of his masonry stove system captured the heat from only periodic burning of wood. It would then spread out that heat over a longer period for a fairly constant temperature. Because of this it only needed to be lit in the mornings and in the evenings. This type of residential (or interior space) heating system is referred to as a kakelugn (in English, a cocklestove) in Swedish. It is a type of "contra-flow stove" which the Chinese have made into a Kang bed-stove.

Cronstedt wrote and had published several books. Among these were,

• 1767 - On a new installation of stoves for firewood saving.