Artificial light is a metaphor for absolute control. By refusing to let in any natural light, Aylmer maintains perfect control over the substances in his laboratory. In lieu of the sun, he uses chemical lamps to illuminate his experiments:
Aylmer, excluding the sunshine, which would have interfered with his chemical processes, had supplied its place with perfumed lamps, emitting flames of various hue, but all uniting in a soft, impurpled radiance.
The lamps' seductive beauty also suggests the obsessive nature of Aylmer's pursuits. Everything he creates revolves around beauty. Everything he uses to create new and beautiful objects must be aesthetically pleasing. Just as he strives to make his wife divinely beautiful by eliminating any trace of human imperfection, he likewise tries to perfect his chemical experiments by eliminating any trace of Nature. However, as suggested by the effect of sunlight on chemicals, this beauty is unnatural.
Sunlight represents the inevitable influence of nature. After Aylmer administers the elixir, Georgiana faints, and he opens the curtain to let in the sun:
He drew aside the window curtain and suffered the light of natural day to fall into the room and rest upon her cheek. At the same time he heard a gross, hoarse chuckle, which he had long known as his servant Aminadab’s expression of delight.
Here, the reappearance of natural light represents his loss of absolute control. The word "suffered" suggests Aylmer's reluctance to permit any trace of nature into his laboratory. He takes great pains to avoid Nature in any form. But the sunlight itself seems gentle as it "rest[s]" on Georgiana's cheek. The contrast between the gentle sunlight and the "gross, hoarse" chuckle of Aminadab makes evident the ugly reality of Aylmer's laboratory. And if Aminadab represents the earthly side of humanity, his laughter could also be interpreted as another metaphor for Nature's ultimate victory.
