In Germany, stained glass development continued with the inter-war work of Johan Thorn Prikker and Josef Albers, and the post-war achievements of Joachim Klos, Johannes Schreiter and Ludwig Shaffrath. This group of artists, who advanced the medium through the abandonment of figurative designs and painting on glass in favour of a mix of biomorphic and rigorously geometric abstraction, and the calligraphic non-functional use of leads, are described as having produced "the first authentic school of stained glass since the Middle Ages". The works of Ludwig Schaffrath demonstrate the late 20th-century trends in the use of stained glass for architectural purposes, filling entire walls with coloured and textured glass. In the 1970s young British stained-glass artists such as Brian Clarke were influenced by the large scale and abstraction in German twentieth-century glass.