If one wishes to prevent the formation of a pigment, formalin solutions must be buffered to a pH of >7.0.

• A. True
• B. False
• C. Not enough information
• D. Always

Answer: (B)

Formalin pigment forms when formalin becomes acidic during fixation, so avoiding acidic conditions prevents the pigment. Keeping the fixative at neutral or near-neutral pH is the practical approach, typically using buffered formalin around pH 6.8–7.0. Requiring the pH to be above 7.0 isn’t necessary and can introduce other fixation artifacts; the important point is to prevent acidity, not to push the solution into alkaline territory.