With regard to an initiator of a redox type, there may be listed an initiator of a combination where a sulfonic acid/sulfonate radical is able to be generated among the combinations of an oxidizing agent such as persulfate, perchlorate, silver salt, copper salt and iron (III) salt with a reducing agent such as sulfite, hydrogen sulfite, hyposulfite, pyrosulfite, triethanolamine and iron (II) salt.