Light skin of UVA can penetrate deeply into the dermis in persons with light skin pigmentation with little protective melanin pigment. The characteristic of fair skin, red hair, and freckling is associated with high amount of pheomelanin, little amounts of eumelanin. This phenotype is caused by a loss-of-function mutation in the melanocortin 1 receptor (MC1R) gene. However, variations in the MC1R gene sequence only have considerable influence on pigmentation in populations where red hair and extremely fair skin is prevalent. The gene variation’s primary effect is to promote eumelanin synthesis at the expense of pheomelanin synthesis, although this contributes to very little
Earth pigment the color can be deepened by heating (calcination) in a process known as "burning", although it does not involve oxidation but instead dehydration. Earth pigment Earth pigments are naturally occurring minerals containing metal oxides, principally iron oxides and manganese oxides, that have been used since prehistoric times as pigments. The primary types are ochre, sienna and umber. Earth pigments are known for their fast drying time in oil painting, relative inexpensiveness, and lightfastness. Cave paintings done in sienna still survive today. After mining, the mineral used for making a pigment is ground to a very fine powder (if not already