Metallic effects

Metallic effects are increasingly popular for pre-finished steel roof and wall cladding products. Adding aluminium flakes to the basic coating creates a sparkly finish. The aluminium flakes, similar in shape to cornflakes but microscopic in scale, reflect back or
scatter the light which falls upon them. This reflection generates the sparkle over and above the background solid colour, and will alter depending upon the viewing angle or level of lighting.

However metallic effects can create their own difficulties. The flakes need to be distributed evenly to ensure a consistent appearance, which is achieved by careful preparation of the paint pre-application. The flat-shaped flakes can orientate themselves differently during their application, or ‘laydown,’ and must be controlled. Finally, the presence of the flakes makes it more difficult to measure the colour electronically, so a consistent coating operation is needed.

The choice of flakes and their application have a major impact on the finished effect. Small flakes give a smooth sheen, medium-sized flakes give a silk or satin effect and larger flakes give a high sparkle. Aluminium flakes are available in a range of sizes from less than 10 µm to over 100 µm in length. In a product such as Colorcoat® PVDF, which is only 27 µm thick, the flakes are in the range of 10-25 µm giving a smooth metallic appearance.

To ensure colour consistency on a single elevation, it is important that pre-finished steel from the same batch is used for all the cladding.