Variation of clay brick colors and mechanical strength as affected by different firing temperatures

Abstract

This study was conducted to quantitatively determine the effect of firing temperature on color formation and to assess the relationship between mechanical strength and color components of clay bricks. Redness index, chroma, hue and color difference (∆E) of bricks fired at 700 to 1050°C in steps of 25°C under free access of air were measured with a colorimeter. Relations between temperature and each of the redness index and color difference indicated that reddening of clay bricks was the main reason of color difference that occurred after 975°C. A highly significant inverse relationship occurred between hue and firing temperature. Hue was the most significant color component describing the variability in strength of clay bricks (R2 = 0.88) and may be used as a quality indicator for clay brick strength. Key words: Brick, redness index, color difference, chroma, hue, firing temperature.