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.
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.
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.
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 →