If mercuric oxide is used as oxidant, the solution must be boiled for the reaction to take place. Other oxidants do not need to be boiled, and oxidation will take place at room temperature over a few days. Although they will oxidise at room temperature, solutions containing sodium iodate may be boiled to ripen more efficiently. Simply bring to the boil for a few minutes, then allow to cool. They are usable immediately.
Half oxidation is a term used to describe partial oxidation of hematoxylin to hematein.
These solutions have an extended life because they are usable before full conversion takes place. Throughout their life, oxidation of hematoxylin and further oxidation of already converted hematein continues. They do not become unusable until oxidation proceeds so far that insufficient hematein remains to give acceptable staining. Chemical half oxidation seeks to emulate this process by adding sufficient oxidant to convert only half of the hematoxylin to hematein. Oxidation will then continue as for a naturally ripened solution.