At a chemistry level, glass is not a smooth surface. Under an electron microscope, it's a landscape of pits, ridges, and micro-fractures that trap airborne minerals, dust, and organic film. The reason your traditional soap-and-squeegee cleaner leaves streaks isn't operator error — it's that the surfactants in the soap are physically incapable of leaving a truly residue-free surface at that molecular scale.
How DI water works
Deionised water is water that has been passed through a two-stage cation and anion resin bed, which swaps every dissolved mineral ion in the water for pure H⁺ and OH⁻ ions. The result: water with a total dissolved solids (TDS) reading of essentially zero — often measured at less than 1 part per million. Municipal tap water, by contrast, typically measures 200–400 ppm.
Why zero TDS matters
Water with zero dissolved solids is chemically 'hungry' — it aggressively bonds to any dissolved solid it encounters. When applied to glass, DI water lifts the mineral, organic, and particulate film off the surface without needing surfactants. When it dries, it evaporates completely, leaving nothing behind. No soap residue. No mineral spots. No streaks.
The equipment behind the science
A commercial DI system has four components: (1) a sediment prefilter to strip particulates ≥5 microns, (2) a carbon block to adsorb chlorine and organics, (3) a reverse osmosis membrane that rejects 95%+ of dissolved solids, and (4) mixed-bed deionising resin that scrubs the final ions. Bespoke's rigs also carry an in-line TDS meter, calibrated weekly, so every crew knows their water quality before the first pane is touched.
The safety multiplier
The other benefit of DI is delivery. Because the water is chemically 'active,' it doesn't need soap — which means it can be delivered through a carbon-fibre water-fed pole. That pole reaches five stories from the sidewalk. Which means no ladders. Which means no fall-risk claims on your insurance policy. Which is a very good reason for your risk manager to insist you hire a DI-equipped vendor.
