I had to make money and I did make money working for other glass factories at the time. (brooklynrail.org)
Upon his arrival in West Germany, in Willich near Krefeld, Polke began to spend time in galleries and museums and worked as an apprentice in a stained glass factory in Düsseldorf between 1959 and 1960, before entering the Kunstakademie Düsseldorf (Arts Academy) at age twenty. (en.wikipedia.org)
Soon afterwards Polke moved with his family to Willich, near Krefeld, in North Rhine - Westphalia, before beginning an apprenticeship in a stained glass factory in Düsseldorf — an experience that may have encouraged the emphasis on light and transparency that dominates much of his work. (theguardian.com)