If sections intended for a specific stain show hematoxylin staining, which of the following is the correct step to reverse this?

• A. Acid Alcohol
• B. Water Rinse
• C. Alcohol Denatured
• D. Acetone

Answer: (A)

The main idea is differentiating or decolorizing to remove unwanted hematoxylin staining. Hematoxylin binds to basophilic structures like nuclei, but some of it can remain on sections that aren’t supposed to be stained for hematoxylin. Using acid alcohol as the differentiating step selectively dissolves and removes this loosely bound hematoxylin, reversing the unintended staining and leaving the tissue ready for the intended stain. Water rinse would just wash away surface stain but not differentiate; alcohol denatured and acetone are non-specific solvents that can disrupt other aspects of the tissue, so they aren’t the right tools for this selective decolorization.