Illustration of the ionization of important elements in the He-rich, O-rich, Si-rich, and Fe-rich shells for the models shown in Fig. 11 (the same color coding is used to differentiate the volume filling factors: black for 100%, blue for 50%, and red for 20%). Different symbols correspond to different elements. The smaller the volume filling factor, the smaller the species ionization. In some cases, clumping causes only a marginal reduction (as for the He shell), but in others the effect is strong (for example, for O in the O-rich shell).