ANALYSIS
Lighting Up the Darkness of Black Anita Fehr BYK-Gardner GmbH – Geretsried, Germany
anita.fehr@altana.com
The spectro2guide Pro, the latest member of the spectro2guide family, was developed by BYK-Gardner GmbH to accurately measure black and describe its undertones. It is the only spectrophotometer on the market that is capable of measuring colour and gloss as well as predicting the long-term colour stability of a sample.
C
arbon black is a material with a long history whose production dates to the early civilizations of mankind. Initial uses can be traced back to ancient China, the early Egyptians, and India since
the days before Christ. The demand for carbon black was particularly driven by the invention of the printing press in the fifteenth century.
Today carbon black is found in all aspects of modern life. It is used in inkjet printer ink, as reinforcements for natural and synthetic rubber and as the active agent in electrically conductive plastics. Probably the widest and best-known application is the usage as a pigment in paints, coatings and plastics to impart a deep black colour, because it has higher tinting strength compared to iron black or organic pigments. Means, not all black is the same.
Definition of blackness In general, black is a colour that results from the absence or complete absorption of visible light. Leading carbon black manufacturers promote carbon black pigments that absorb up to 99.98% of light. The higher the absorption coefficient of a medium, such as a black coating, the higher is the achieved blackness value (My). Deep black coatings can have an undertone – bluish or brownish. A deep black colour with a bluish undertone in the full tone is perceived as richer, darker and more brilliant than with a brownish undertone. Two samples with the same blackness (My) and different undertone (dM) can be perceived as different blacks, whereas the sample with blue undertone will be perceived as deeper black. For this reason, black with a blue undertone is often preferred in technical applications, such as for the topcoats in the automotive industry. The hue-dependent degree of blackness is referred to as “jetness” (Mc). The calculation for the blackness value My is based on the tristimulus A detail of the “Olympia” painting (Édouard Manet, 1863). Not all black is the same: in this work the artist succeeded in applying the black tone of the servant and the cat on a black background.
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N. 70 - JULY/AUGUST 2021 - international PAINT&COATING magazine
value Y and a 10° observer: Blackness My My = 100 log (100 / Y) This determines only the lightness of a sample without considering the coloured undertone. As the undertone of a black colour has an impact
