Clas Alströmer was originally an agriculturalist who studied sheep breeding in six European countries from 1760 to 1764. After his return to Sweden he joined the East Indian Company of Göteborg, an internationally known business firm. Later he formed a partnership with his brother Patrick. During the American Revolution the brothers, through the East Indian Company, planned a great trading venture in metal and cloth products to the American colonies, borrowing considerable capital for the purpose. As soon as peace was established, however, the market for Swedish goods collapsed, and the East Indian Company suffered a loss of 300,000 riksdalers ( Svenskt Biografiskt Lexikon ).

Trained in the management of cloth manufacturing, Patrick Alströmer became director of manufactures of Alingsås, a town northeast of Göteborg, in 1758; four years later he visited cloth-manufacturing facilities in St. Petersburg and other Russian cities. After a catastrophic fire in Alingsås ruined Patrick's business, he accepted an invitation from his younger brother Clas to enter into partnership with him. Patrick became director of the East Indian Company in 1777, and the two brothers were raised to the rank of baron the following year (same).