Sodium Hypochlorite NaOCl

Sodium hypochlorite (chemical formula NaOCl) is the chlorine-based oxidizer that does the actual cleaning work in household bleach and in commercial soft-wash chemistry. Household bleach typically contains 5-6% NaOCl. Pool-grade liquid chlorine ranges from 10% to 12.5%. Commercial soft-wash applicators dilute the concentrate down to a working solution somewhere between 0.5% and 3% NaOCl at the surface, depending on what they’re cleaning.

The chemistry is straightforward: NaOCl in solution releases hypochlorous acid, which oxidizes the cell walls of bacteria, algae, mold, and lichen, and breaks down the organic pigments that make stained surfaces look stained. That’s why a soft wash on a stucco wall lifts the green-black algae streaks instead of just pushing them around — the chemistry is killing the organism and bleaching the pigment at the same time.

Two things determine whether NaOCl is the right call for a given job:

1. Substrate tolerance. NaOCl is safe on stucco, cement, concrete, most painted surfaces (when freshly applied paint has cured), asphalt shingles, and most single-ply roof membranes. It’s NOT safe on bare metals, fresh wood, certain stains, or unsealed natural stone where the chloride can drive into the pore structure.

2. Surrounding conditions. Overspray onto plants needs to be neutralized with a pre-wet and post-rinse. Vehicles within overspray range need to be moved or covered. Aluminum window frames and fencing get pre-wet so chloride doesn’t dry on them.

Material safety: NaOCl mixed with any ammonia-based product releases chloramine gas, which is hazardous. The SDS for every NaOCl product warns against this and crews are trained to never co-mix.