Erich Buchholz occupied a central place in the international avant-garde in Berlin in the 1920s. His earliest prints are influenced by the work of the German Expressionists, particularly Franz Marc. In the period immediately after the First World War his art shifted from an expressionist style to non-objectivity. He is now regarded as one of the pioneers of geometric abstraction in Germany.
Check out the huge, experimental photographic process work from artist Brittany Nelson. Using old-style chemistry techniques like silver gelatin emulsion and mordançage, Nelson creates these beautiful and fascinating works. Many more on her site here.
Also, check out this video here of Nelson speaking about her work and process.