The ceremony in Frankfurt Cathedral lasted several hours and John Frederick found it very impressive.

He added his private library to the existing collection and from 1751 onwards, he allowed the general public to access it once a week.

He considerably extended the collection of the "Princely public library Rudolstadt", founded in 1748, be purchasing scientific literature and numerous valuable books, incunables and oriental manuscripts.

[3][4][5] On 4 October 1760, John Frederick granted a license to operate a porcelain factory to Georg Heinrich Macheleid.

John Frederick himself acted as a director for this company, which still exists under the name of Aelteste Volkstedter Porzellanmanufaktur.

On this occasion, John Frederick officially named the building Gymnasium Friedericianum and added a position teaching mathematics and physics.

John Frederick married on 19 November 1744 in Eisenach to Princess Bernardina Christina Sophia of Saxe-Weimar-Eisenach (1724–1757).