By the late 19th century the growing plastics and house paint industries needed increasing quantities of better quality oxides and at the same time many of the traditional natural sources were showing signs of becoming depleted. This problem was solved in 1921 when patents were granted for the synthetic iron oxide process that is used today. These synthetic colors were called Mars colors because Mars was the god of iron and the planet Mars was red like several of the first oxides. These synthetics were important for many reasons. Since the natural ochres were clays, the actual color component was as little as 20% with the rest being various contaminants. This meant that natural ochre is always slightly browner than the synthetic Yellow Oxide. Besides the more pure coloration, Yellow Oxide also has the property of absorbing light in the UV range and so their usage in plastics and coatings protects the polymers thus extending the life of products used outdoors. The higher proportion of iron oxide in the synthetic Yellow Oxide was thus important for many industrial applications where UV resistance was required including for the growing house paint industry. Electronics is another field with a growing demand for iron oxide pigments as they form the basis of the magnetic data storage discs in hard drives. The need for purity is one of the main reasons why the synthetic pigment has almost completely replaced natural ochre in the industry field and the visual arts. The synthetic oxide has also mostly displaced the natural ochres for artists paint too with the purity of color being the driving reason behind the change.
Chemical Description: Trans synthetic iron oxide
Pigment Numbers: PY42
Lightfastness Rating: ASTM I
Pigment Opacity: Transparent
Paint Opacity: Transparent