Rainwater & Patience: The Lowest-Impact Way to Clean a Fragile Old Stone

headstone cleaning in Virginia | headstone cleaning in Norfolk Virginia

I’ll never forget the day I found my great-great-grandmother’s headstone, it was July, and I was tramping through a tiny cemetary in upstate New York, looking for the plot I’d only seen in a faded 1920s photo. Took me an hour. When I finally spotted it, my heart sank. The marble slab was almost black with lichen, moss was creeping up the sides like green fingers, and the inscription—her name, her birth year—was completely unreadable. I sat down on the grass next to it, feeling stupidly emotional. This woman had crossed the Atlantic in steerage, buried three kids, lived through the Civil War. And here she was, forgotten under a crust of grime.

I wanted to clean it. Bad. But I also knew—from a disastrous attempt with a wire brush on my own backyard flagstone—that old marble is soft, porous, and easily ruined. So I did what any nervous, broke historian would do: I went home, researched for three days straight, and came back with a bucket of rainwater and a whole lot of patience. That headstone is readable now, and it’s still intact. No etching lost. No pitting. No damage. That’s why I’m writing this. Not because I’m an expert—I’m just a lady who messed up once and then got it right. Here’s how you can too.

Why Rainwater? (And Why Tap Water Can Be Your Enemy)

Tap water isn't pure. Most municipal water has chlorine, fluoride, and dissolved minerals—calcium, magnesium, the works. On an old stone, those minerals can leave white deposits called efflorescence. Ugly. They can also react with the stone's surface over time. Rainwater, though? It's soft. Naturally distilled. No additives. I collect mine in a clean plastic barrel I got from a hardware store for twenty bucks. Let it sit for a day so any dust settles. Then I pour it into a spray bottle. Simple. If you don't have a barrel, you can buy distilled water at the grocery store for a buck a gallon. That's fine too. The point is: no extra chemicals, no minerals. Just water.

What You'll Actually Need (A Short, Honest List)

You don't need much. I'm serious. Here's my kit: a spray bottle (the cheap kind, just make sure it's clean), a soft natural-bristle brush (I use a horsehair brush—nylon can scratch), a plastic scraper (like an old credit card, for lifting thick moss), and a bucket of rainwater. That's it. Oh, and a few microfiber cloths for blotting. I also bring a small spray bottle of D/2 Biological Solution—it's a pH-neutral, non-ionic cleaner that's safe for marble, limestone, and sandstone. It's the only commercial product I trust. You don't need bleach, you don't need vinegar, you don't need anything harsh. Avoid those. They eat away at the stone's surface. I know—I learned the hard way.

The Step-by-Step: Go Slow, Go Gentle

First, spray the stone with rainwater until it's wet. Let it sit for five minutes. This softens the biological growth. Then, using your plastic scraper, gently lift off any thick moss or lichen. Don't pry—just slide it off. Next, dip your horsehair brush in rainwater and scrub the stone in small circles. Light pressure. You're not scrubbing a pot. You're coaxing dirt out of pores. Rinse the brush often. If you hit a stubborn spot, spray on some D/2 and wait ten minutes. Then scrub again. Keep the stone wet the whole time—dry scrubbing can scratch. After you're done, rinse thoroughly with rainwater. Blot with a microfiber cloth. Then walk away. Let it dry for a day. You might need to repeat the process a second time. I did. Took me three visits over two weeks. Worth it.

When to Stop (And When to Call a Pro)

This method works for light to moderate biological growth—moss, algae, lichen, dirt. But if the stone is flaking, crumbling, or has deep cracks? Stop. Don't touch it. Seriously. Wetting a crumbling stone can make it fall apart faster. If the inscription is already gone, scrubbing won't bring it back. And if the stone is sandstone that's turned to powder, you need a conservator, not a bucket. I've seen people 'clean' a stone until it loses it's carved letters. Heartbreaking. Know your limits. For my great-great-grandmother's stone, the marble was solid—just encrusted. That's the sweet spot. If you're unsure, take a photo and email a local preservation society. They'll tell you if it's safe.

Frequently Asked Questions

Q: Can I use rainwater if I live in a city with acid rain?

A: Good question. Honestly, if you're in a heavy industrial area, your rainwater might be slightly acidic (pH around 5.5 or lower). That's still safer than tap water with chlorine, but ideally you want neutral water. So if you're worried, buy distilled water from the store instead. It's pH-neutral and cheap. I do that when I'm cleaning stones near my cousin's place in Pittsburgh.

Q: How long do I need to let the rainwater sit before using it?

A: I let mine sit for about 24 hours in a covered barrel. That lets any dust or particles settle to the bottom. You can use it sooner if you're impatient, but you risk getting grit in your spray bottle. And grit on a stone? That's basically sandpaper. Not good. So wait a day.

Q: Is D/2 Biological Solution really neccessary, or can I just use rainwater alone?

A: You can start with just rainwater and a soft brush. For really light dirt, that's enough. But for lichen or black algae, rainwater alone won't cut it. D/2 is specifically made to kill biological growth without damaging stone. It's not soap—it's a biocide. I use it sparingly, maybe once every few years. One bottle lasts forever.

Q: What if the headstone is made of granite? Can I still use this method?

A: Granite is much harder than marble or limestone, so you could use a stiffer brush and even a little more elbow grease. But honestly, I still stick with rainwater and a soft brush for granite too. Why risk it? Granite is tough, but it can still get scratched by abrasive dirt. So go gentle. Same method works fine.

Q: I tried scrubbing with rainwater and nothing happened. What am I doing wrong?

A: You're probably not letting the water soak long enough. Spray it on, walk away for ten or fifteen minutes. Let the water penetrate. Then scrub. If that still doesn't work, you might have a layer of 'crust' that's mineralized, not just biological. That needs a poultice—basically a paste of D/2 and water applied overnight. I can write a seperate post on that if people want.