Heijenbrock is sometimes called the 'painter of iron and fire'. Initially he was a journalist / draftsman. After traveling to the Belgian Borinage in 1898, he started painting the working man in a world of technology and machines. He found his motives in mines, factories, harbors and iron smelters. He chose not to display the desolate life of the workers, but the heroism of their work, coming from a holy belief in the progress that technology would bring to man. The invention and application of artificial light fascinated him as special achievements of technology.