Old Masters’ paintings were mostly brown because earth colors were the only lightfast pigments available. Found all over the earth in various shades of brown and muted shades of red, orange, yellow and green, earth colors have been on artists’ palettes for more than 40,000 years.
At the special request of Nathan Olivera, Robert Gamblin formulated a contemporary version of Asphaltum that is true to its historic working properties but, unlike traditional formulations, is both lightfast and permanent. Gamblin’s version, much to Olivera’s delight, captures not only Asphaltum’s qualities but also its “earth energy.”
In the studios of the Old Masters, painters pushed against the limitations of their colors. Sienna and Umber are key colors in creating effects of depth like Caravaggio’s chiaroscuro or Leonardo’s sfumato with its almost imperceptible transitions from light to dark. The famous “Terra di Siena” is a hydrated iron oxide from Tuscany. It contains silicates and aluminates that increase the transparency of the pigment.
Umber is found in sites where naturally occurring manganese dioxide combines with iron. Umbers and other pigments containing manganese make quick-drying oil colors. Burnt Sienna and Burnt Umber are made by roasting earth pigments until the desired reddish colors are produced.
Natural earth pigments often have uneven color and must be washed and processed into small particle sizes. This labor-intensive processing led to a demand for synthetic iron oxides that were developed as Mars colors in the late 18th century.
There is some discussion about why synthetic iron oxides were first produced, especially when so much pigment was then available in earth mines. The most logical explanation is commercial painters demanded consistency in color and texture for the emerging house paint industry. The British started to build homes with wood but they still wanted their houses to look like brick. Also, through the manufacturing process, shades can be changed. “Mars” was an internationally recognized word for iron.
A hundred years after the Masters’ great era, there was a revival in their techniques. Asphaltum was used when painters wanted to artificially age their painting to make them look like an Old Master could have painted them. Organic in nature, the original Asphaltum was coal black and crumbly. The pigment was not ground into oil but rather melted into oil and turpentine. Among the few transparent earth colors, Asphaltum was used in glazing and shading. But by the end of the 18th century, painters were dissuaded from using the color because it caused paintings to fade and deteriorate at an alarming rate.
Two hundred years later, painters’ interests have turned again toward the techniques of Renaissance masters. Like their predecessors, contemporary painters are pushing against the limitations of their colors. Often painters ask if earth colors are less transparent today than hundreds of years ago. The answer is YES. Today’s earth pigments are more opaque because the once rich deposits in Siena, Corsica and Cyprus are nearly mined out. Today’s earth colors must be mined from various locations and mixed together to achieve consistent colors. The bulk of earth pigments are used to color concrete for stucco and other building materials. The result is a rise in cost and a decline in transparency.
The late 20th century has produced the first significant change in iron oxides with the invention of transparent Mars colors for the automobile industry. These colors are made by hydrating earth colors, a process by which opaque colors are made transparent. As painters we have come full circle. The prized transparent earth reds of antiquity have returned to our palettes.