Etched Swirl Sky

German ätzen, to etch — past-participle of etch. As a color modifier, etched implies a clear-and-precisely-incised quality, the crisp color of Rembrandt-and-Dürer hand-pulled etching-print fine-line incised-image. Sits at the crisp-and-incised end of the grid, parallel to engraved and inscribed in usage.

Middle English swirlen, to-whirl-in-eddies. As a color modifier, swirl implies a curling-and-eddying-and-spiraling quality, the visual register of Van-Gogh-Starry-Night-and-Hokusai-Wave-swirl hand-curling-and-eddying-and-spiraling Van-Gogh-Starry-Night-and-Hokusai-Wave-and-Art-Nouveau swirled-and-curling-and-eddying-and-spiraling surfaces under Van-Gogh-Starry-Night-and-Hokusai-Wave-and-Art-Nouveau brush-stroke-and-cresting-wave-and-vine-tendril nocturne-light. Sits at the modifier-and-mood end of the grid, parallel to eddy and stir in usage.

The blue of a clear sky at noon — produced by Rayleigh scattering, the preferential dispersion of shorter wavelengths through atmospheric molecules. Air itself is colorless; the color we see is sunlight scattered toward our eyes by every cubic kilometer above. The reference shade is mid-latitude noon under a high pressure system: a clean, slightly green-shifted blue with the luminous depth of light scattered across an entire hemisphere of air.