Solid colours

Solid colours are relatively straightforward. A plain finish in a particular colour can be explained using one of a number of standards. The longstanding British Standard, BS 5252 for building, still persists as a reference for 237 well-accepted or traditional colours. However, this standard has largely been superseded by Pantone, RAL or NCS.

Pantone references are typically used in the printing industry, and so tend to represent brighter shades produced by four-colour printing. Whilst a pre-finished steel product can be matched against these, it may have to use pigment types which do not weather well. It is accepted that paper will fade in sunlight, which is not a concern for printed publications. However, the outside of a building, exposed to the elements, may lose its appearance far sooner than desired. Therefore, the Pantone references should be avoided in preference to others, whose shades are more achievable and relevant to a construction product.

Both the RAL and NCS systems are widely used to describe pre-finished steel products for roof and wall cladding, so much so that a number of industry standard colours are in fact direct translations of these

Unfortunately, it gets more complicated with simple shades, such as white. Corus has matched thousands of shades, such that our internal systems contain numerous versions of white. It is important for the building designer to see actual metal samples, rather than relying on printed or reference systems, no matter how high quality they are. This is because of an effect called metamerism.

Metamerism refers to the situation where two colour samples which match when seen under one light, appear different under another. In the laboratory, using a calibrated light box, a strong visual match can be given in addition to an electronic match. However, once in natural or artificial light, differences between the two may become apparent. These are frequently associated with changes in texture or surface condition altering the appearance.