In the Verhoeff's Van Gieson technique, why is staining time critical?

• A. Picric acid continues the differentiation of the elastic fibers
• B. Hematoxylin differentiates nuclei
• C. Eosin differentiates collagen
• D. Ferric chloride fixes the tissue

Answer: (A)

In this staining sequence, the emphasis is on keeping a crisp color separation between elastic fibers and the surrounding tissue. Elastic fibers are first stained black with the Verhoeff component, then differentiated to sharpen their contrast. The Van Gieson counterstain, which includes picric acid and acid fuchsin, not only colors collagen and other elements but also continues the differentiation process started earlier. Picric acid helps suppress non-elastic elements and reinforces the distinction so elastic fibers stay dark while collagen and other structures take on their contrasting colors. If this step is left too long, the elastic fibers can begin to fade and background elements may over-stain; if too short, the contrast between elastic fibers and collagen won’t be as clear. That’s why staining time is critical in this technique.