What the National Park Service Standards Say About Old Markers

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I still remember the day I found my great-great-grandmother’s headstone. It was a gray Saturday in October, and I’d spent two hours bushwhacking through a forgotten corner of an old cemetary in rural Ohio. The stone was half-sunken, covered in a thick crust of moss and lichen. I actually sat down next to it and cried a little. Not because I was sad — well, maybe a little — but because I had no idea how to clean it without wrecking it. Took me three tries. Worth it.

That’s when I started digging into what the pros do. And let me tell you: the National Park Service has some of the smartest, most careful standards for old cemetery markers I’ve ever seen. They’ve been studying this stuff for decades. Their guidelines aren’t just for rangers in fancy uniforms — they’re for anyone who wants to clean a grave without accidentally sandblasting history into dust. So here’s what I learned, straight from the NPS playbook.

Why the NPS Standards Matter for Regular Folks

You might think the National Park Service cemetery preservation standards only apply to places like Gettysburg or Arlington. Nope. Their research covers everything from 1700s slate tablets to 1950s granite. The key principle? Gentle is always better. They say: 'Do no harm.' That’s it. That’s the whole philosophy. I love that. They’ve tested all kinds of cleaners and tools, and they’ve found that most household products — the stuff you’d grab from under the sink — will eat away at old stone fast. Marble is especially soft. Limestone too. Sandstone crumbles if you look at it wrong. So the NPS says: use only what’s proven safe. For me, that meant buying a bottle of D/2 Biological Solution. It’s a pH-neutral, non-ionic cleaner that kills organic growth without damaging the stone. I was skeptical. But after a few weeks, the lichen just flaked off. Magic.

The Tool List: What the NPS Says to Use (and Skip)

Here’s the blunt truth from the NPS: skip the wire brushes, steel wool, and pressure washers. Those tools scratch the stone’s surface, which makes it hold dirt and grow more moss. Big mistake. Instead, they recommend soft natural-bristle brushes (horsehair is ideal) and plastic scrapers for stubborn crud. Wooden tongue depressors work great too. I used a plastic putty knife on my great-great-grandmother’s stone — gently, at an angle — and it lifted the crust without gouging. Also: never use harsh household chemicals like bleach or strong acids. Those react with the minerals in the stone and cause permanent yellowing or pitting. Stick with the D/2. It’s what the National Park Service uses at many historic cemeteries. I bought a gallon for about $40. Lasted me two years.

The Step-by-Step Routine (NPS-Approved)

The NPS has a simple method, and I followed it exactly. First: soak the stone with water. I used a garden sprayer — the kind you pump. Let it sit for ten minutes. That softens the biological gunk. Second: apply the D/2 Biological Solution. Don’t dilute it. Just spray it on straight. Let it sit for 15–20 minutes. Third: gently scrub with your soft brush. I used circular motions, light pressure. The lichen came off like wet paper. Fourth: rinse with water. No pressure washer — just a gentle spray. Let it dry naturally. That’s it. I did this on a cloudy day so the solution wouldn’t dry too fast. The NPS warns against cleaning in direct sunlight. Learned that the hard way on my first attempt. Left a white residue. Had to do it again. Never again.

When to Call a Pro (and When to DIY)

Not every old marker is a DIY job. The National Park Service cemetery preservation standards say: if the stone is flaking, cracked, or already falling apart, don’t touch it. Seriously. One wrong scrub can make it crumble. I of a friend who tried to clean her great-uncle’s sandstone marker with a stiff brush. The date came off in her hand. She still cries about it. For fragile stones — especially marble from before 1900 — hire a trained conservator. Look for someone who follows NPS guidelines. Prices vary, but expect $200–$500 for a full cleaning. That sounds like alot until you realize you’re saving a piece of history. For solid granite or slate that’s just dirty? Go ahead. Just use the D/2 and a soft brush. I’ve done it five times now. Works every time.

Frequently Asked Questions

Q: Does the National Park Service allow bleach on old headstones?

A: No. Absolutely not. The NPS specifically says to avoid household bleach because it creates a chemical reaction that can yellow the stone and weaken it over time. They recommend only pH-neutral, non-ionic cleaners like D/2 Biological Solution instead.

Q: Can I use a pressure washer if I keep the pressure low?

A: The NPS strongly advises against any pressure washing on historic markers. Even low pressure can force water into cracks and cause spalling (that’s when the surface flakes off). Stick with a garden hose and a low-flow spray nozzle. That’s what the pros use.

Q: What if the headstone is covered in black crust or lichen that won't budge?

A: The NPS says patience is key. Apply a biological cleaner like D/2, let it sit for 20–30 minutes, then gently scrub. For really stubborn spots, you may need two or three applications over several weeks. Never use a wire brush or an abrasive pad. I had a lichen patch that took four treatments. It came off eventually.

Q: Are there any NPS-approved alternatives to D/2 Biological Solution?

A: Yes. The NPS also recommends a mild solution of distilled water and a few drops of pH-neutral dish soap (like Dawn or Ivory) for routine dust and dirt. But for biological growth like moss, lichen, or mildew, D/2 is their top pick because it kills the roots without harming the stone. Other options include Orvus WA Paste (a non-ionic cleaner used by many conservators).

Q: How often should I clean an old headstone according to NPS standards?

A: The NPS suggests cleaning only when neccessary — maybe every 5 to 10 years for most stones. Over-cleaning can wear down the surface. If it’s just dusty, leave it. If you see green growth starting, that’s the time to act. I clean my family’s markers once every three years, but that’s only because they’re in a damp, shady spot.