Light from the original image will shine on the photoconductor. When this occurs the dark regions of our original will not transmit light on the photoconductor. The bright parts will cause the photoconductor to act as a conductor in those regions and the surface charge will no longer be present. The toner, essentially ink, is a black powder that makes the final image on the xerox paper. The regions of the photoconductor that still have charge attract the oppositely charged toner.
Opposite charges attract, which keeps the toner on the photoconductor.
The fuser binds the toner to the paper using heat. To do this, she uses an optical pyrometer, an instrument through which the lava flow is viewed. Superimposed on the image of the lave is that of a current-carrying wired within the pyrometer. The current, and thence the temperature, of the glowing hot wire can be varied with a dial on the instrument. The vulcanologist visually compares the color of the wire and that of the lava to get the needed temperature reading.