Bubbles have become a hallmark for David Medalla. In 1963, he made Cloud Canyons, tall columns of wood and Formica with a special bubble-generating machine that slowly extrude thick snakes of soap bubbles. In 1966 came Cloud Windows, in 1971 Cloud Discourse and Cloud Fruits; a marriage of mechanical and organic forms which methodically produce random, meandering sculptural wedges of bubbles and countless other memorable extrusions of great thick snakes of soap. Other works include; sand machines, mud machines, smoke machines and a project to lift the Great Wall of China on to the moon.