On 27 January 1810, he obtained a royal license to establish and operate a cloth factory in Copenhagen.
[1] Modeweg was married on 2 September 1805 in Trinitatis Church to Marie Magdalene Louise Bock (1783–1843).
She was the daughter of tobacco spinner Johan Carl Bock (1750–1805) and Frederikke Lovise Braad (ca.
She was the daughter of sailing master Hans Gullich Tangen and Johanne Elisabeth Franck.
His widow Anna Elisabeth, Modeweg (née Gudmann) sold the company in 1872 to the wholesalers Carl Albeck (1830–1905) and William Salomonsen (1842–1900).