salt) could drive more dye onto the fiber, but surely not seven times as much! The answer lies in the diffusion equilibria. Dye in the bath and dye in the fiber are trying to establish an equilibrium. But every time a dye molecule reacts with the fiber, its place has to be taken by a molecule of dye being transferred out of the bath and into the fiber, in an attempt to re-establish the equilibrium. Even if equilibrium is never reached, there is always a driving force to attract dye out of solution and into the fiber as long as dye continues to react.