Samples were run in duplicate.
Details of sample preparation and applications for the source
and special clays were presented previously (Doğan
et al. 2006). To determine the color properties of the
materials, L*
, a*
, and b*
values and whiteness index (WI)
were measured under the standard illuminant D65 by
using the CIELAB system (CM-700d Konica Minolta
Series Spectrophotometer). The spectrophotometer was
calibrated to the perfect white diffuser by a ceramic plate
with tristimulus values X = 90.3, Y = 92.1, Z = 105.7 and
chromaticity coordinates x = 0.3135, y = 0.3196. The pH,
water soluble substance, acid-soluble carbonate, and acidsoluble
iron of the samples were determined according to
the Turkish Standards adapted to European Norms TS EN
ISO 3262-10 and other Turkish Standards TS 2973 and TS
10521.