D/2 Biological Solution is the cleaner the National Park Service and the Department of Veterans Affairs use on government headstones — a quaternary ammonium biocide that kills stone-dwelling growth without acids, bleach or salts. When conservation headstone cleaning names its chemistry, this is it.
What it is and how it works
D/2 is a biocide formulated for historic masonry: it kills algae, lichen, mould and mildew at the root, penetrating the growth rather than burning its surface. It contains no bleach, no acids and no salts — the three ways cleaners destroy porous stone — and rinses without leaving residues that recrystallise later.
Its adoption on national cemetery markers is the practical credential: institutions responsible for millions of irreplaceable stones chose it, tested it and kept it. Worth saying plainly, though: using the same product those programmes specify is not the same as being part of them. We are a local cleaning business that follows published conservation practice. Nobody has certified or endorsed us, and any company telling you otherwise is selling something.
Why non-ionic and pH-neutral matter
Two properties do most of the safety work, and both are easier to understand by looking at what they avoid.
pH-neutral means the solution is neither acidic nor strongly alkaline. That matters enormously on marble and limestone, which are calcareous — calcium carbonate, the same mineral that acid descales from a kettle. An acidic cleaner does not clean calcareous stone; it dissolves a layer of it, taking the crisp edges of the inscription with it. Vinegar, lemon juice, brick cleaners and rust removers all sit in that category, and all of them will visibly soften carved lettering on old marble. A neutral cleaner leaves the mineral alone and works on the organism instead.
Non-ionic means the active molecules carry no net charge, so they do not leave ionic residues behind in the pore network when the water evaporates. That is the exact failure of bleach: the hypochlorite reacts and disappears, but the chloride stays, cycles with humidity and crystallises inside the stone until the surface breaks apart. A non-ionic formulation has nothing left to crystallise. It rinses out or breaks down, and the stone is chemically where it started.
The third property is one people rarely think about: it works without force. Every mechanical method — wire brush, abrasive pad, pressure washer — removes growth by removing a thin layer of the stone the growth is attached to. Chemistry that kills the organism in place removes nothing but the organism.
Why it looks slow, and why that is right
Applied and agitated, D/2 lifts some staining immediately — but its real work continues for weeks. The biocide keeps killing embedded growth, and rain progressively carries off the dead material. A treated stone at six months looks markedly better than at six minutes.
That delayed result is the sign of the correct mechanism: chemistry doing the removal instead of abrasion. Anything that gets a stone instantly white did it with force or acid, and the stone paid.
What is actually happening over those months
Lichen is the reason the timeline is long. A lichen is a fungus and an alga living as one organism, and it does not sit on stone the way dirt does — it anchors into the surface with root-like structures that penetrate the pores, and on marble it will slowly etch its own footprint into the face. When the colony dies it is still mechanically attached. It has to weather off.
So the sequence after a treatment runs roughly like this: the loose surface growth and staining lift on the day, the colony dies over the following days and weeks, the dead structure loses grip through successive wet-dry and freeze-thaw cycles, and rain takes it away piece by piece across a season. Trying to accelerate the last step by scraping is how you get a pale scar shaped exactly like the lichen that was there — the stone under the colony has weathered differently for decades, and forcing the material off takes surface with it.
The same principle governs biological growth everywhere on a property. It is why roof cleaning is a chemistry job rather than a scrubbing job, and why telling lichen apart from moss and algae changes what you should expect from a treatment. On a headstone the stakes are simply higher, because there is no replacing the surface.
What D/2 will not do
It is a biocide, and it is honest about its lane. It will not remove iron staining — the orange bleed that comes from a rusting pin, a wire brush used decades ago, or run-off from an iron fence. It will not remove paint, tar, or old adhesive from a previous repair. It will not restore lettering that weather has eroded away; where the carved edge is gone, better contrast is the whole of what cleaning can give you.
It also will not undo salt damage already loaded into a stone by earlier bleach cleanings. Nothing applied at a graveside will. And it will not make an unstable marker safe — on flaking, sugaring, delaminating or cracked stone, the right answer is no cleaner at all until a conservator has stabilised it.
Southeast Missouri: why our markers need it
This region puts steady biological pressure on stone. Humid summers, river-valley damp, and heavy morning fog off the bottoms keep surfaces wet for long stretches, and the mature oak and pine cover over most older burying grounds means shaded stones may never dry fully between rains. Add heavy spring pollen and leaf drop, and a north-facing marble face around Patton or Marble Hill can carry an established colony within a few seasons of being cleaned.
Freeze-thaw then works in our favour and against us at once. Between December and March a treated stone goes through dozens of cycles, and every one of them helps break dead lichen free — which is part of why a spring treatment often looks best the following summer. The same cycling is what destroys a stone that has salt in it, which is the whole argument for a chemistry that leaves none.
Practically, this shapes how we work a cemetery. Rural burying grounds towards Fredericktown, Piedmont and Ironton are a drive, so we treat a section in one visit rather than a stone at a time, and we bring our own clean water instead of relying on a site spigot — much of the water in this Ozark limestone country is hard and iron-bearing, and iron-rich water leaves its own stain on a white marble tablet.
Part of a method, not a magic bottle
D/2 belongs inside conservation practice: assess the stone’s stability first, pre-wet with clean water, apply, agitate with soft brushes only, rinse well, and let time finish. The product is safe; carelessness with sound technique still is not.
On unstable, flaking or cracked markers, no cleaner is appropriate until the stone is stabilised. The assessment is as much the service as the wash. Two more parts of the method get skipped more often than they should. Brushes must be soft natural or soft nylon — never wire, never a scouring pad, never anything abrasive, because metal both abrades the stone and leaves iron particles that rust in the pores. And permission comes before water: confirm with the cemetery, which will often have written rules about what may be applied to a marker, and with the family, if the stone is not yours to clean. The full sequence, from assessment to rinse, is worth reading before you buy a bottle of anything.
Common questions
Can I buy D/2 myself?
Yes. It is sold openly to the public, and a family that wants to care for its own plot can absolutely use it. The product is the easy part. The assessment, the permission and the discipline to use a soft brush and stop early are what actually protect the stone.
Does it need to be diluted?
Follow the manufacturer’s directions on the container rather than anything you read online, including here. Different stone conditions and different levels of growth call for different handling, and the label is the authority.
Will one application be enough?
Often, on a stone with light to moderate growth. Heavy lichen on a rough weathered face may need a second treatment after the first has had months to work — which is another reason to judge a result in the following season rather than on the day.
Is it safe around grass and plantings?
It is formulated to be used in cemeteries, which is a large part of why those programmes adopted it, and normal graveside use has not given us trouble with turf. We still rinse generously and avoid soaking planted beds, because there is no reason to test the limits of anything on someone’s family plot.
Why not just use a household cleaner and save money?
Because household products were formulated for surfaces that can be replaced. Bleach loads salt into the pores, acidic cleaners dissolve calcareous stone outright, and detergents leave residues that hold dirt. The cost difference is small and the stone is not replaceable.
We carry and use D/2 on every marker we touch. Photos of the stone get you an honest assessment before anything else. Read more about conservation headstone cleaning →