Coatings 2023 , 13 , 195
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( a )
( b )
( c )
( d )
Figure8. CIE L*a*b* coordinates for the investigated substrates and coatings. ( a , b ) L*-a* and L*-b* coordinated for the KB substrate. ( c , d ) L*-a* and L*-b* coordinated for the KP substrate. Nevertheless, considering Δ E* (CIE2000) values (Table 3), values below 2 are generally considered not perceivable by the human eye. Only highly filled experimental coatings in- volving the HPH 40 latex showed color variations slightly higher than 2 for both substrates considered in this work. Additionally, commercial coatings are characterized by the lowest color variation. The most interesting value, however, is related to the glossiness of the surface (Figure 9). Indeed, regardless the coating, the substrate generally achieved higher glossiness values. It can be observed how increasing kaolin amounts—for almost every experimental coating— significantly reduces the glossiness of the coating. This is not true for H40K 100, where the coating defects (as of Figure 2) strongly influenced the measurements, as highlighted by the high standard deviation.
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