5 ноября, 2015 
Pokraskin Chemical purity: The selective absorption of visible light by a pigment is predominantly decided by its chemical structure; therefore, chemical purity is one of the important factors that produces consistent color.
Particle size: In general, below a certain optimum particle size, pigment particles are optically active through their entire mass, and absorption is no longer a function of particle size; thus, it remains constant with further decrease in size. Above this optimum particle size, the amount of light absorbed is proportional to the surface area of the particles, and therefore, by increasing the particle size above the limiting value, the total absorption of light decreases per unit mass of pigment. In general, smaller particles are brighter in color. Also, by decreasing the particle size, the shade of color is shifted towards medium wavelengths. For example, greener yellows or yellower reds can be obtained at smaller particle sizes.
Crystal structure: In certain cases, chemically identical pigments existing in different crystal forms (also known as polymorphisms) may exhibit a different hue. Pigments that clearly show the effect of polymorphism on hue are quinacridone pigment (Pigment Violet 19), phthalocyanine pigment (Pigment Blue 15) and lead chromates.
Опубликовано в рубрике 