Surface decalcification is achieved by exposing the tissue surface to which condition?

• A. 1% hydrochloric acid for 15–60 minutes
• B. 5% hydrochloric acid for 5–10 minutes
• C. 10% formic acid for 30 minutes
• D. 0.5% nitric acid for 2–4 minutes

Answer: (A)

Surface decalcification relies on applying a dilute acid to just the outermost mineralized layer so that the surface becomes soft enough to section without removing calcium from the entire specimen. A mild hydrochloric acid solution provides that controlled, superficial decalcification: it softens the surface enough to cut cleanly while leaving the deeper tissue largely intact. If the acid is too strong or exposure too long, decalcification would penetrate deeper, risking over-decalcification, loss of structural detail, and poor stain quality. Other options that use higher concentrations or different acids tend to remove calcium more quickly or more thoroughly, which is not desirable when you want only surface softening.