A Comparison of Historic and Modern Pigments

Are modern substitutes for ancient or expensive pigments the same color as the original ones? Many artists pose this question and the opinions vary from person to person.  While many pigments have been produced for centuries, others have had a distinct and limited lifespan. Colors once celebrated for revolutionizing the art world are now just entries in books and historical records.  

Many pigments have had dubious histories. Being an artist and handling dangerous and in some cases lethal compounds, should have given an artist pause to consider alternatives.  However, knowledge of the depth of the inherent danger of pigments, to some degree, was misunderstood. In the 15th through 17th century, industrial progress had limited impact on the art materials trade. However, the industrial revolution would introduce a wide variety of new materials with pigments derived from advancements in chemistry and modern methods of industrial production.

A number of artists lament the passing of the pigments that were standards in the ancient world. Due to the dangers inherent in some pigments, the high cost of manufacturing or toxic byproducts that are produced when making certain pigments, many well known colorants have been discontinued. So, do the modern, safer substitutes come close to match the color of their ancient counterparts?

Visual comparisons by the human eye and a suitable, uniform light source is one method to assess how good an old, now discontinued pigment relates to a new substitute.  Another way is to take a measurement using a device called a spectrophotometer that assesses the color reflectance at wavelength segments within the range of visible light detectable by a human eye. A spectrophotometer provides the reflectance of a color that is be expressed in mathematical terms and can be analyzed and plotted as a graph.  This removes the subjectivity in judgement or lack of color sensitivity that humans can inject into making color assessments. In addition, color is related to the light source in which it is viewed. Vary the color temperature of the light and a pigment can look different.  A spectrophotometer maintains a constant, calibrated light that eliminates that bias.  Let's examine how three historic pigments match spectrally with modern equivalents.

Lapis Lazuli, the natural mineral version of ultramarine blue, is measured against the modern French ultramarine blue. The spectral curve of natural lapis appears to have more violet undertones and stronger orange and red reflectance than modern synthetic ultramarine. This sample of natural lapis is more violet and warmer overall in hue than synthetic ultramarine. The two pigments are chemically the same and share many visual similarities. Natural lapis has inherent inconsistencies since samples come from different locations with variations in the color and amounts of trace materials that are naturally found in conjunction with lapis.

The spectra of Cadmium Red compared with Vermilion, made from mercuric sulfide, provides some insight into the difference each pigment maintains. Vermilion displays more yellow and orange and thus accounts for the familiar red-orange characteristic of the pigment. Cadmium Red appears to show dominance in the red portion of the spectrum with warm undertones in the orange and yellow regions. Cadmium Red is very stable with exposure to light and does not react chemically as Vermilion has demonstrated over the centuries by turning dark due to a reaction of the pigment to neighboring colors as well as the atmosphere.

Comparing the spectra of Cobalt Blue and Smalt, a blue glasslike pigment used during the Renaissance and for several centuries beyond, a strikingly difference can be seen when paired with Cobalt Blue. The smalt contains reflectance in the violet, blue and green areas that cause the color to have a cool bias. Both blue pigments have a characteristic warm red “tail” at the far end of the visible spectrum. Because of the red reflectance, Cobalt demonstrates that it is warmer when compared to Smalt.