 Washing with water or alkali treatment after staining causes base catalyzed hydrolysis and removal of the pendant positively charged side chains and the resulting compound is Phthalocyanine Blue, which forms a blue water-insoluble dye precipitate.The precipitates are so robust that they withstand harsh conditions like PAS or other counterstaining and also dehydration and embedding treatments (in contrast toluidine blue is partially extracted away during dehydration).This unleachability is the chemical basis of the ingrain dyeing for which AB (Ingrain blue 1) was originally designed by the dye industry.