Wet & Forget vs D/2 on Headstones: Which I Reach For

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I still remember the day I found my great-great-grandmother's headstone, it was buried under ivy and moss, so bad I almost walked right past it. Took me three tries to even read the name. Elinor. The stone was a soft grey marble, and the lichen had made these bumpy, crusty patches that looked like old cornflakes glued on. I spent that afternoon on my hands and knees with a soft brush and a bucket of water, just getting the big stuff off. My back hurt for a week. Worth it.

That got me started on this whole headstone-cleaning obsession. And let me tell you, I've tried alot of products. Some work great. Some are total duds. The two I get asked about most are Wet & Forget and D/2 Biological Solution. People want to know which one is better, which one is safer, which one actually works on the tough stuff. So here's my honest take, based on years of scrubbing, waiting, and occasionaly messing up. Big mistake I made once? Using something I shouldn't have. Never again.

Let me break down both products, so you can pick the right one for your stone.

What These Two Products Actually Are

Wet & Forget is a spray-on-and-leave-it product. You wet the stone, spray it on, and walk away. It works slowly over weeks or months. The idea is that rain activates it, and it keeps working over time. It's originally made for outdoor surfaces like roofs, decks, and fences. But people use it on headstones too. The main ingredient is a quaternary ammonium compound. Not super harsh, but not the gentlest thing either.

D/2 Biological Solution is made specifically for headstones and monuments. It's a non-ionic, pH-neutral formula. That's the gold standard for stone cleaning. It also uses biological action to eat organic stains, but it works faster — often in minutes to hours, not months. It comes as a concentrate you mix with water, or a ready-to-use spray bottle. I use the concentrate because it's cheaper per batch.

Big difference: D/2 is formulated to be safe on all stone types, including marble, limestone, sandstone, and granite. Wet & Forget is safe on many surfaces, but I've heard some people say it can leave a residue on porous stone if not rinsed well. I've never had that problem, but I always rinse thoroughly after.

Speed of Results: Patience vs Instant Gratification

Here's where they really split. Wet & Forget is a slow burn. You spray it on, maybe in spring, and by fall you start seeing resultes. Lichen turns yellow, then flakes off. Moss shrinks. It's like watching paint dry, but in reverse. I used it on a granite marker that had green algae streaks. Took about three months before I could really tell a difference. But it worked. No scrubbing.

D/2 is the opposite. You spray it on, wait 10-15 minutes, and the gunk starts dissolving. Seriously. I did a test on a sandstone footstone that was covered in black mildew. Sprayed D/2, waited maybe 20 minutes, and used a soft bristle brush to gently lift the crud. Came right off. The stone underneath looked almost new. Not bleached, just clean.

If you're doing a family reunion cleanup and want immediate results, D/2 is your friend. If you're not in a rush and want to set it and forget it, Wet & Forget is fine. Just don't expect a miracle overnight.

Safety for Different Stone Types

This is the part that matters most. Not all headstones are equal. My great-great-grandmother's is marble. Soft, porous, scratches easy. So I'm paranoid.

D/2 is pH-neutral and non-ionic. That means it won't react with the stone's chemistry. It's safe on marble, limestone, sandstone, slate, granite — you name it. I've used it on a 200-year-old sandstone marker with zero issues. No etching, no color change, no residue. The manufacturer actually guarantees it's safe for historic stones. That's a big deal.

Wet & Forget is also fairly gentle, but it's not specifically made for stone. It's a general outdoor cleaner. The active ingredient can be slightly alkaline. On hard, dense granite? Fine. On soft limestone or old marble? I'd be careful. Some folks online report that it left a whitish film on porous stone that took a while to rinse away. I've never seen that myself, but I only use it on granite or modern concrete markers.

My rule: If the stone is historic, soft, or you're not sure what it is, go with D/2. Always. Don't risk it.

Cost and Availability: Which is Easier to Get?

Wet & Forget is everywhere. Home Depot, Lowe's, Amazon, even some grocery stores. A gallon of concentrate runs about $25-30, and you dilute it with water. One gallon makes a lot of spray. For a single headstone, you might use a quart of mixed solution. Cheap.

D/2 is harder to find locally. I usually order it online. A quart of ready-to-use spray is about $20. The concentrate (makes 8 gallons) is around $40-50. So upfront, D/2 costs more per ounce. But because it works so fast, you use less product per cleaning. I find a quart of ready-to-use lasts me 4-5 cleanings on average-sized headstones.

If you're on a tight budget and patient, Wet & Forget is fine for granite. If you want the best for historic or soft stone, D/2 is worth the extra money. I keep both in my garage. Wet & Forget for the granite family plot, D/2 for the old marble ones.

Frequently Asked Questions

Q: Can I use Wet & Forget on a marble headstone?

A: Technically yes, but I don't recommend it. Marble is soft and porous, and Wet & Forget can leave a residue that's hard to rinse off completely. Plus, the alkaline ingredients might dull the surface over time. For marble, stick with D/2 Biological Solution — it's pH-neutral and made specifically for stone.

Q: How long do I need to wait between applying D/2 and rinsing?

A: Usually 10-20 minutes is enough for light moss or algae. For heavy lichen or black mildew, I let it sit 30-45 minutes, then gently brush with a soft nylon brush and rinse. Don't let it dry on the stone — always rinse with clean water. I use a garden sprayer or a hose with a gentle spray nozzle.

Q: Will Wet & Forget kill lichen on headstones?

A: It can, but it's slow. Lichen is tough. I've seen it take 4-6 months for Wet & Forget to fully kill and loosen lichen. D/2 works much faster — often in one application. If you've got thick lichen, I'd go with D/2. Patience is a virtue, but I don't have that much patience.

Q: Do I need to scrub with either product?

A: Not always. Wet & Forget works without scrubbing — that's the whole point. D/2 also works without scrubbing on light growth, but for heavy buildup, a soft brush helps speed things up. Never use wire brushes, steel wool, or anything abrasive. Soft nylon or natural bristle only. Scratching the stone is permanent.

Q: Which product is better for preventing future growth?

A: Both have some residual effect, but Wet & Forget is better at prevention because it stays active on the surface for months, reactivating with each rain. D/2 is more of a one-and-done cleaner. If you want long-term prevention, Wet & Forget is the better choice. I use it on granite markers in shady areas where moss keeps coming back.