Mechanical and Optical Properties of Soft Pastel with Varying Body Pigment Ratio

Abstract

Soft pastel, lightly pressed with body pigment, has various colors close to the color pigments. We built the hypothesis that a certain volume of body pigment provides delicate nuance of color, tone, and texture to soft pastels. We examined the effect brought by two types of body pigments regarding color and strength respectively. Experimental results supported our hypothesis. About color, we obtained lower numerical values of Value and Chroma when we used porcelain clay than calcium carbonate (CaCO₃). In other words, calcium carbonate produces light and bright color, and porcelain clay produces tint or neutral color. Concerning strength, applying porcelain clay, fracture stress was further increased than CaCO₃. Furthermore, we examined the relationship between the drawing medium (pastel) and the support medium (paper etc.). The result showed that the weaker the drawing medium strength becomes, the more the pigmenting (coloring) becomes capable with weak pressure. But easy pigmenting does not always mean generating rich and various color tones. Those facts suggested the possibility that optimum numeric value in medium strength would be found out, which enable us to perform broader expression.