How do you clean a 100-year-old headstone?

How do you clean a 100-year-old headstone?

Century-old headstones require significantly more caution than routine outdoor cleaning, since decades of weathering often leave the stone more fragile than it looks. Start by tapping the stone gently — if it sounds hollow, stop immediately and consult a professional conservator rather than proceeding. If it’s solid, rinse thoroughly with plain water first, then apply a biological cleaner formulated specifically for historic stone, such as D/2 Biological Solution, the product used by Arlington National Cemetery and the National Cemetery Administration. Let it sit for the recommended time, then gently work it in with a soft natural-bristle brush, never a wire or hard-bristled brush, and never bleach, ammonia, or acidic cleaners, all of which can permanently damage old stone. Never use a pressure washer. Rinse thoroughly and pat dry with a soft cloth — patience matters more than force here.