I keep the direct transmittance completely clean and put all the crust into the shallow-angle roughness. That way the view through stays crisp, but the second the camera rakes across the pane, you catch that dry, milky bite of real salt.

Living on the Zeeland coast, I've learned to dial that roughness map back to pure fiction—the second you make it honest, someone asks why the facade looks broken.

Give it just enough tooth to catch the evening light, but never name the grime—call it 'atmosphere'. The second a client realizes it's salt, the fantasy breaks.