However, a year before his final exam, he decided for the first time to try working with paint,[5] which resulted in his decision to study fine art and graphic design instead.
According to Yerka, during his period studying in the academy he was pressured by his instructors to eschew detail and realism in favor of the fashion of the times - but did not relent, adhering to the meticulous classic Flemish technique that still typifies his work.
In the morning and afternoon he had to do tests, projects and attend lectures, and during the evening he was given a couple hours to work at a painting that was shown only to his family and friends.
His subject matter ranges from odd beasts to whimsical landscapes incorporating extraordinary architecture, and includes imagery gleaned from his childhood, such as his grandmother's kitchen.
In 1990, Yerka received a contract with Hollywood producer Renee Daalder to design figures, monster-machines and surreal landscapes for the science fiction film Strawberry fields, based on the Beatles song of the same name.