In both of these works the candlelit setting had a realist justification. Viewing sculpture by candlelight, when the contours showed well and there might even be an impression of movement from the flickering light, was a fashionable practice described by Goethe. In the orrery demonstration the shadows cast by the lamp representing the sun were an essential part of the display, used to demonstrate eclipses. But there seems no reason other than heightened drama to stage the air pump experiment in a room lit by a single candle, and in two later paintings of the subject by Charles-Amédée-Philippe van Loo the lighting is normal.