Color changes of porcelain surface colorants resulting from firing

Differential loss of chrome from surface colorants during firing can make the prediction of final porcelain color difficult. This investigation was undertaken to assess the color change of nine extrinsic colorants during firing. Colorants were applied to metal-ceramic substrates, and color was measured both before and after firing using a colorimeter. CIE LAB color coordinates were obtained as a measure of the direction and quantity of color change. Color change for yellow (delta E*ab = 4.00) was significantly greater than that for the other groups (delta E*ab = 0.41-1.25). Changes in L*a*b* values for yellow samples were toward those of the controls.