Hematoxylin

Discovered at the end of the 19th century, this Mexican tree extract stains only when oxidized (naturally by aging or chemically) and coupled with a metallic mordant.

It then becomes cationic and will stain anionic acids, like nucleic acids.

The most popular mordant is aluminum and acetic acid is often added to prevent excess oxidation.

Depending on the concentration, the hematoxylin can be used as a regressive stain (overstain and then selectively decolorize). This is how Harris hematoxylin is mostly used. It can also be used as a progressive stain that does not require decolorization but takes longer to stain like Mayer’s and Gill hematoxylins.

In all cases it will have to be submitted to a bluing agent, an alkaline solution like tap water or Scott’ss substitute as its natural red color does not provide enough contrast.

Ferric hematoxylin like Weigert’s is used with two different solutions, hematein and mordant mixed just before use or in sequence.

Nothing has yet been able to replace hematoxylin for nuclear staining than. You just have now to select which one will give you more satisfaction and please your pathologist!