Advantages of Nano Pigments Over Micro Pigments in Obtaining Larger Spectra of Colours in CMYK System

Abstract

Based on the CMYK colour system, it is possible to obtain the full colour spectrum with mixing the four colours – cyan, magenta, yellow and key (black). In this research, ceramic nano pigments including CoAl₂O₄ (cyan), Au (magenta), (Ti,Cr,Sb)O₂ (yellow) and CoFe₂O₄ (key) were mixed together with different ratios and applied on glazed tiles and the colour specifications of the samples were measured. The Colours Software (CSA) was used for predicting the ratios of the pigments for obtaining a target or reference colour. For comparison, equivalent micro pigments, namely CoAl₂O₄, Cd(S,Se):ZrSiO₄, (Ti,Cr,Sb)O₂ and CoFe₂O₄ were also examined. It was observed that using the present nano pigments, it was possible to cover the fourth quarter of the CIELab circle close to a ⁺ axis, while this was not possible with the micro pigments. This was attributed to the blue tint present in Au nano pigment. It was also revealed that reaching the colours of grey, brown and beige shades was possible by both nano and micro sets of pigments, while making orange and yellow colours was difficult. Also, it was revealed that yellow nano and micro pigments did not have thermal stability at high temperatures. The results indicated that nano pigment with 4.592 < a ^* < 15.606 and −1.560 < b ^* < +1.549 had yellow and blue tints and its yellow tint was due to grain growth, but micro pigment showed more red and less yellow tint. The above mentioned a* and b* values indicate the high colour performance of the pigment.

Keywords:

• Ceramic pigments
• Combination
• Nano pigments
• CMYK system