Where the Etihad now stands or near it for the pedants, Clayton Aniline made the base pigment for textile dyes but mainly the blue spectrum. Copper-phthalo-cyanine being the active agent. Textile dyers would then tailor it to their specs, Cortaulds for one, Ila another. Various middle-men would merchant the powder throughout the world, the point I am laboriously trying to make is that each dealer could call it whatever they felt like, furthermore it was produced in batches and therefore was subject to "tolerances" . Not only that the end result was reliant on the substrate it was being used on to be consistent in colour and absorbency.
Ultra-violet exposure then plays a part as a whitening agent. Sky blue is a generic term, the colour of the sky is dependent on many factors, Cambridge blue is not a Bsi patented protected afaiaa so when all is said and done .......... city blue is good for me even though it has been linked to the masonic movement
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