Doing a Second D/2 Pass Weeks Later: When It's Worth It

headstone cleaning in Pennsylvania | headstone cleaning in California

I’ll never forget the first time I tried to clean a really stubborn headstone, it was a beautifull old granite marker in a little cemetary outside of Bozeman, Montana. The family had asked me to photograph it for a genealogy project. I got there, and the stone was just... Green. Lichen had taken over the entire front face, and there were these thick, crusty patches of moss that looked like they’d been there since the 1920s. I did my first D/2 pass, waited the full 15 minutes, scrubbed gently with a soft brush, rinsed. It looked way better. But not great. I packed up, drove the four hours home, and honestly felt a little defeated. Took me three tries. Worth it. That’s when I learned: sometimes one pass just isn’t enough. You need to let the stone rest, let the D/2 keep working, and come back. So let’s talk about when a second D/2 pass weeks later makes sense, and how to do it right.

Why Wait Weeks? The Science of Slow Cleaning

D/2 Biological Solution isn’t a harsh chemical stripper. It’s a biological cleaner that eats organic growth over time. The first application breaks down the surface layer of lichen, moss, and algae. But if the growth is thick or deeply rooted, the D/2 can’t penetrate all the way in one go. Waiting two to four weeks gives the solution time to work deeper into the pores of the stone. The organisms die off, dry out, and loosen naturally. Then the second pass can lift that deeper gunk off way easier. I’ve seen headstones that looked like they were stained forever just... Release the crud after a second pass a month later. Patience pays off.

Signs You Need a Second Pass

Not every stone needs a second pass. But here’s what I look for. If after the first cleaning the stone still has green or black patches that feel rough to the touch (not just stained), that’s a sign. Also, if you see lichen that’s still crusty and raised, even after scrubbing, it’s probably still alive under a thin layer. Another big clue: if the stone dries and looks blotchy — some parts clean, some not — that’s uneven penetration. That’s when I mark my calendar for three to four weeks out. I also pay attention to the wheather. If it’s been rainy, the growth can rebound fast. A second pass after a dry spell is often magic.

How to Do the Second Pass Right

First, don’t assume you can skip the prep. I always do a quick inspection. Is the stone still stable? Any cracks or flaking? If yes, I’m extra gentle. Then I wet the stone with plain water — just from a spray bottle. Then I apply D/2 again, exactly like the first time. Spray it on generously. Let it sit for 10–15 minutes. No more. D/2 doesn’t need longer. Then I scrub with a soft nylon brush (never wire, never metal). I use circular motions, but light pressure. Rinse thoroughly with water. I usually use a pump sprayer with clean water. Then I step back and look. If it’s still not clean after the second pass? I wait another few weeks and try a third. I’ve done four passes on one stone before. That was a 1920s marble with black crust. It came out looking new. But only because I let the D/2 do it's slow work.

When NOT to Do a Second Pass

Here’s the flip side. If the stone is fragile — crumbly sandstone, flaking marble, or any stone with loose layers — a second pass might do more harm than good. Scrubbing again can pull off bits of the stone itself. In those cases, I stop after one pass and just accept the result. Also, if the first pass already removed 90% of the growth and the rest is just light staining, a second pass won’t help. Staining from iron or minerals won’t come off with D/2. That’s a different problem. And finally, if you used any harsh household chemicals on the first pass (please don’t), don’t layer D/2 on top. That can cause chemical reactions that damage the stone. Stick with D/2 from the start, and you’re fine.

Real Results: What to Expect After the Wait

I’ve done this dozens of times now. The second pass usually gets the stone 80–95% clean. The biggest difference is the texture. Before the second pass, the stone might feel slightly gritty or rough where the lichen was. After, it feels smooth. The color evens out. Inscriptions that were barely readable become crisp. I had one client — a woman looking for her great-grandfather’s grave in a rural cemetery in Ohio — and the stone was almost black with soot and moss. First pass turned it a muddy gray. Second pass six weeks later? It was a beautiful light gray granite. She cried. I’m not exaggerating. That’s why I do this. So if you’re on the fence about a second D/2 pass weeks later, just do it. Worst case, it doesn’t help much. Best case, you uncover history.

Frequently Asked Questions

Q: Can I do a second D/2 pass sooner than two weeks?

A: Technically yes, but I don’t recommend it. The D/2 needs time to keep breaking down the organic matter. Doing it too soon just re-wets the same partially dead growth without giving it a chance to loosen. I always wait at least two weeks, and ideally three to four. The longer wait makes the second pass way more effective.

Q: Will a second pass damage the headstone if I scrub harder?

A: It can if you get aggressive. Even on hard stones like granite, scrubbing too hard with a stiff brush can wear down the surface polish. On marble or sandstone, it’s even riskier. Always use a soft nylon brush and light pressure. The D/2 does the work — you’re just helping it rinse away.

Q: What if it rains between the first and second pass?

A: That’s actually fine. Rain won’t wash away the D/2 that’s already soaked into the stone. It might even help by keeping the stone damp, which lets the biological solution keep working. Just don’t apply D/2 right before a heavy rain — it’ll dilute it too much before it can penetrate.

Q: Do I need to reapply D/2 to the whole stone or just the dirty spots?

A: I apply it to the whole stone. Even if only a few spots look dirty, the D/2 will also kill any invisible spores or micro-growth. That prevents the clean areas from getting re-contaminated later. It’s a small extra cost for way better long-term results.

Q: Can I use a pressure washer instead of a second D/2 pass?

A: No. Pressure washers are way too harsh for most headstones, especially older ones. They can blast away the stone’s surface, erode inscriptions, and cause cracks. Stick with the D/2 and a soft brush. It’s slower but it won’t ruin the stone. I’ve seen too many damaged stones from pressure washers. Not worth it.