Iridescent fibres

Iridescence in many of the fabrics that are available commercially is basically a two-colour effect due to the absorption of light from dyes in two differently coloured yam bundles, constructed in such a way that the reflected light comes from one particular bundle in one direction and from another in a different direction. Whilst this is not truly iridescence it is a useful effect, but the process is very limiting on the construction of the fabric. 

A better alternative would be to have fibres that in their own right could show multiple colours based on the direction of view. One model for this is a fibre that consists of a concentric core and a sheath, each made from different types of polymers. For instance, constructing a fibre where one fibre is acid dyeable nylon and the other basic dyeable nylon make it possible to dye the sheath and the core in different colours. The colour change i.e. hue shift) then varies with the angle of incidence of light on the fibre. 

A range of fibres marketed by Meadowbrook Inventions Inc. produce their iridescence in fibres by a tme light interference effect. This is achieved by constmcting the fibre from polymers having different refractive indices, similar to that which results from interference in thin multi-layers of polymer fllms.  

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Artificial organic colouring matters may be in powder, crystals, lumps or more or less aqueous paste. They exhibit various tints often different from those they impart to the fibre they frequently show iridescence and metallic lustre, especially if crystallised. 

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