  The formation of regular precipitate stripes in the wake of moving chemical
reaction-diffusion fronts is investigated. Experiments on the $NaOH+CuCl_2$
reaction in PVA hydrogel yield stripes parallel or slightly oblique to the
front that supplies the precursor of the precipitate. The pattern formation was
modeled by phase separation described by the Cahn-Hilliard Equation. Computer
simulations reproduced the parallel and the oblique striping as well. Stripes
perpendicular to the front are unstable and cannot be observed, in complete
agree with the experiments.
  Pattern formation in the wake of quenching fronts has also been investigated
computationally, and compared to the previous results. It has been shown that
below a certain front speed stripes perpendicular to the front will appear.
Moreover, they will bend so that their growing end to be kept perpendicular
even if the front changes its direction. This result can be important in
designing several nanotechnologica lithographical processes.
