The first photographs were created when a sheet of glass was coated with collodion, a sticky substance containing silver halide crystals that produced metallic silver when exposed to light. Soon, photographers used plastic triacetate, which was more versatile and pliable than glass. Decades later, collodion was replaced by a gelatin that swelled in liquid, and therefore held tightly to the base as the processing chemicals reacted with the silver halides. After the gelatin dried, it shrunk back to normal thickness, creating a shape and position of the image that were more true and undistorted than ever before. We can conclude from the information in this passage that collodion