In this experiment, we used different addition ratio of the pigment and straw, to improve the decorative effect of the finishing touch while finding the kinds of clay colors taking on many sophisticated images, through the comparison between the various colors and textures of the surface. (1) To test the plaster material, added were the pigment of Red, Yellow, Black, and Green by the percentages of 0.5, 1, 1.5, 2, and 2.5, respectively, followed by the analysis of the color changes of the plaster material using the Photoshop (RGB). The results showed the bigger the addition ratio of the red color is, the higher the numeral values of RGB after it dried. However the brightness after drying didn't showed a big difference depending on the addition ratio. With the addition of the yellow pigment, the color difference between after and before drying was bigger in the order of Blue, Green and Red; the brightness increasingly rose while the saturation changed little. (2) When we scratched the plaster surface with U and V shape carving knives, the U knife didn't make a clean shape digging around the clay plaster material but with smooth textures, while the V knife made a clean cut, which represents its readily use in terms of the decorative function of the clay plaster. (3) In an experiment the surface texture was tested with different lengths and additions ratio of the straw, addition of 2cm straw by 1, 2, and 3% presented the most appropriate surface of the plaster.
