Professor for Landscape Painting
After 1860, his technique underwent a change into what is considered his mature style. The paintings were more tactile, the paint was applied with more texture and the brushstrokes were less dependent on the subject matter represented. In parts of some paintings, Achenbach increasingly dispensed with detailed figures. This change in technique may have to do with the influence of Gustave Courbet. His favorite subjects continued to be Italian landscapes and peasant scenes, which he enhanced and idealized with his lighting.
In March 1863, Achenbach became the Professor for Landscape Painting at the Kunstakademie Düsseldorf. Accepting this represented a social elevation and also financial security. It also appears to be in contradiction to his earlier opposition. However, since Friedrich Wilhelm Schadow had left the office of Director in 1859, the conflicts both within the academy and also between the academy and the independent artists had diminished. The appointment of Achenbach to a position was a conscious political decision reflecting the new direction of the Düsseldorf Academy, to bring about a conciliation with the independent artists.
In the same year, Achenbach was named a Knight of the Legion of Honour by Napoleon III and from 1863 to 1868 his painters were shown at the Salon in Paris. Alongside the Order of Guadelupe from Emperor Maximilian I of Mexico i 1866 and the Knights Cross, First Class from the Order of St. Michael from the jury for the International Art Exhibition in Munich in 1869, this was among the greatest honors hof his career. Such recognition for artists during this period was not uncommon, but they contributed significantly to Achenbach's fame, confirmed his recognition as an artist and were important for his commercial success.
Achenbach followed Hans Gude as professor of landscape painting at the academy. After 1866 he taught one of the highly regarded "Master Classes." Among his best-known students are Gregor von Bochmann, Arthur Calame, Themistokles von Eckenbrecher, Arnold Forstmann, Theodor Hagen, Louis Kolitz, Ascan Lutteroth, and Carl Seibels. To his students, he emphasized above all the decisive role of light and dark for the composition of paintings. For him it was more important than the choice of subject. Consequently, he advised his students to familiarize themselves with the paintings of J. M. W. Turner. He also recommended the works of his brother Andreas.
During his professorship, Achenbach continued to undertake many trips. These included long stays in the Teutoburg Forest and Switzerland. In 1871 he and his family spent almost nine months in Italy, including Castellammare di Stabia, Amalfi, Capri, and Ischia, and several weeks in Sorrento. During this time Theodor Hagen and Albert Flamm took his place at the academy.
After 1860, his technique underwent a change. The paintings were more tactile, the paint was applied with more texture and the brushstrokes were less dependent on the subject matter represented. In parts of some paintings, Achenbach increasingly dispensed with detailed figures. This change in technique may have to do with the influence of Gustave Courbet. His favorite subjects continued to be Italian landscapes and peasant scenes, which he enhanced and idealized with his lighting.