In the Periodic Schiff stain, the blue hematoxylin counterstain is too intense and masks the magenta red colour of the Schiff's reaction. Which is a documented cause?

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In the Periodic Schiff stain, magenta color comes from the Schiff reagent reacting with aldehyde groups, while blue from hematoxylin provides a counterstain for tissue context. If the hematoxylin staining is too long, the blue counterstain becomes very intense and can overwhelm or mask the magenta signal, reducing contrast and making the Schiff color hard to see. This over-staining of hematoxylin is a documented cause of the problem. Shorter hematoxylin staining would lessen the blue intensity and improve contrast; having no hematoxylin would remove the blue background and not create masking; using a lighter Schiff reagent would diminish the magenta color itself, not cause masking by the blue counterstain.