4. Fixing of the images
Images obtained by photobleaching are generally not stable. The bleached dye returns to its original color after variable times depending on the structure of the complex and that of the binder in which they have been dispersed. The molecules of the complex have a relatively large size compared to other components of the emulsion and it is easy to freeze them in their configuration by crosslinking the binder. As the bleaching involves a steric reorganization of the molecule with displacement of relatively large groups, it is prevented by the formation of crosslinks distributed over the entire volume occupied by the molecule.