Height of the exposed layer divided by the disk radius z₁/r against disk radius r. Silicate grains are plotted in grey, carbon grains in black. Large grains are settled close to the midplane. In the exposed layer above z₁, carbon grains can be oxidised, indicated in red. The range of vertical dust movement is shown by blue arrows. Grains stay for t_res in the exposed layer, and within t_mix, material from the exposed layer is well-mixed with material from the midplane.