He was also a teacher and director of the Academy of Fine Arts of Ghent and the Académie Royale des Beaux-Arts in Brussels.
[3] Through his art, teaching and his leadership of the Académie Royale in Brussels he exerted an important influence on the next generation of Belgian artists, including his pupil Théo van Rysselberghe.
[5] As he spent much of his time as a youngster drawing the scenes of his native town, his father sent him in 1836 to study at the Académie Royale des Beaux-Arts in Brussels.
Portaels studied at the Academie under Navez with other brilliant students such as Charles de Groux and Joseph Stallaert.
In his spare time, he studied the old masters in the Louvre and visited the Paris salons to seek inspiration from the new artistic trends in France.
[3] The financial reward connected to the prize allowed him to travel to Italy where he stayed in Venice, Florence and Rome.
He continued to feel the pull of the Orient and travelled successively to Morocco, Algeria, Egypt, Lebanon, Judea, Spain, Hungary and Norway.
[3] On his return to Belgium in 1847 Portaels was appointed Director of the academy in Ghent to succeed Henri van der Haert who had died.
Portaels was in demand as a portrait painter and also received many orders from the Belgian state and religious institutions, including the frescoes decorating the old Chapel of the Brothers of Christian Doctrine for which he used the innovative water glass technique.
[3] Portaels remained removed from the conventions of his time in the way he treated his subjects, as exemplified in his classic vision of the exotic theme of the Oriental woman.
[11] He returned numerous times to the aesthetic type of the 'Oriental woman' which he depicted with typically arched eyebrows and languid, almond-shaped eyes.
Portaels and Jean Baptiste van Eycken, also a pupil of François-Joseph Navez, helped launch the monumentalism movement in Belgium.
[14] Portaels used the water glass technique at the old Chapel of the Brothers of Christian Doctrine (demolished in the 19th century).
Portaels also used this technique to decorate the tympanum of the Church of St. James on Coudenberg in Brussels with a scene showing the Blessed Virgin as a comforter of the needy.
Portaels also decorated the drawing room of the Brussels home of his friend doctor Nollet with scenes from the history of medicine.
[15] Portaels eminent place in the history of contemporary Belgian art is due to his influence as a teacher of the next generation of Belgian artists such as Belgian painters Emile Wauters, Théo van Rysselberghe, Edouard Agneesens, Léon Frédéric, Jef Leempoels, Isidore Verheyden, Jean Delville, Xavier Mellery, Alfred Verhaeren, Antoine Van Hammée, Ernest Blanc-Garin, Jean Mayné, Josse Impens, Vanden Kerkhoven, Henri Vanderhecht, Eugène Joseph Adolphe Van Gelder, Fernand Toussaint, Albéric Coppieters, Louis Maeterlinck, Jacques de Lalaing, Jakob Smits, André Hennebicq, Camille Van Mulders, Anton Lacroix, Franz Meerts, Sophie Pir, Emile Charlet, Léon Houyoux, Dutch painters Jan Toorop and the Oyens brothers, the French painter Fernand Cormon, the sculptor Charles van der Stappen and the architects Ernest Van Humbeeck and Charles Licot.