The first pigments used by humankind.
The ancient remnants of human creativity are vivid portrayals of animals, humans, and spirits, crafted using ochres, with evidence of their usage dating back as far as 250,000 years ago.
Ochres, naturally occurring earth pigments containing iron, offer a diverse palette of yellow, red, and brown hues. In their most primitive form, these pigments could be easily gathered or excavated and subsequently ground against a harder rock, with the addition of water transforming them into a fluid medium. As civilizations evolved, the refinement of this process involved washing ochres to eliminate impurities, followed by drying and finely grinding them into powder.
Yellow ochres, recognized as an impure form of iron oxide known as limonite, could also undergo transformation through roasting. The application of moderate heat would shift the yellow tones to orange, while stronger heat would result in a vibrant red color. The roasted red ochres, often referred to as 'burnt' (e.g., burnt Sienna), boast a spectrum of hues created through this controlled heating process.
In contrast, naturally occurring red ochres contain a higher concentration of anhydrous iron oxide, specifically hematite, providing a rich array of shades, hues, and levels of transparency. The ancient practice of using ochres not only serves as a testament to our artistic heritage but also highlights the resourcefulness and ingenuity of early civilizations in harnessing the vibrant colors embedded in the earth itself. Understanding the history of pigments, their origins and applications informs not only the discipline of conservation, but is a cornerstone element of art authentication.
The creation of bone white involved the incineration of bones in open fires until all organic matter was consumed, leaving behind the bone in an ash-like state. Traces of bone white's utilization date back to Neolithic times, establishing it as one of the earliest pigment colors crafted through transformative processes.
While virtually any type of bone could be employed, historical recipes exhibited a particular preference for specific bone sources. Hartshorn white, a variant of bone white, was specifically derived from the antlers of the male European red deer, commonly known as a hart. Antlers, being bone structures, were obtained annually as deer shed them during winter, undergoing collection and preparation similar to other bones.
The primary components of bone white consist of a blend of calcium phosphate and calcium carbonate, resulting in a gritty whitish-grey powder when ground. This texture, slightly abrasive in nature, found practical applications, such as its incorporation in the preparation of paper for silverpoint drawings. When mixed with warm liquid rabbit-skin glue, bone white served as a priming coat, enhancing its adherence to surfaces.
Beyond its role in artistic mediums, a paste composed of water and bone white emerged as a polishing agent for metal sculptures and silverware. The versatility of bone white, stemming from its ancient origins, reveals its adaptability in various creative and practical endeavors throughout human history.
Similar to the production of bone white, the creation of bone black involves placing fragments of animal bones into a crucible and subjecting them to intense heat by surrounding them with blazing coals. However, a crucial distinction lies in the process to prevent the bones from turning to ash – the vessel is covered to eliminate air exposure. The absence of oxygen during the exposure to high heat transforms the bones into carbonized char, which is subsequently cooled and pulverized using a mortar and pestle.
Evident in prehistoric, Egyptian, Greek, and Roman art, bone black continued to be a prominent pigment during the Middle Ages and Renaissance. Dutch painters of the 16th century, in particular, harnessed its dense physical characteristics to vividly portray garments. Medieval artisans further refined the manufacturing process by washing the pigment with water, filtering it, and grinding it to a finer consistency on a stone slab, intensifying the color.
The quality of preparation and the type of bone used in the process determine the range of black hues produced, spanning from blue-black to brown. In the earlier periods, bone black wasn't as widely employed as charcoal black, likely due to the hardness of the raw material and the difficulty of grinding it to a fine powder. Although bone black is still utilized today, it is often marketed under the name "ivory black." Genuine ivory black was traditionally created by charring waste ivory pieces, but its availability was limited due to the scarcity of ivory. With the prohibition of the ivory trade, the pigment sold under the name "ivory black" now typically consists of bone black with added carbon content to enhance its darkness.
Whether employed independently or blended with ochres to enhance their vibrancy, the utilization of chalk significantly broadened the spectrum of available colors. Abundantly accessible and easily transformable into a fine powder, chalk held a dominant position until the Ancient Greeks introduced lead white. Chalk, a soft mineral known as calcite or calcium carbonate, originates from the fossilized remains of microscopic phytoplankton algae, forming thick and expansive deposits. The iconic white cliffs along the southern English coastline exemplify renowned chalk formations.
Various manifestations of chalk, such as English whiting, Bologna chalk, and Champagne chalk, have been utilized since the early Renaissance to create a traditional gesso ground. Gesso, a luminous white plaster surface, found application in constructing intricate timber panels for church altarpieces. It served to harmonize the object's appearance and provided a smooth priming coat onto which gold leaf or egg tempera paint could be applied.
With the ascent of oil painting in the 15th century, artists transitioned from solid timber to flexible woven linen canvases as their painting surfaces. The rigid gesso was replaced by pliable oil primers colored with lead white, as chalk tends to become nearly transparent when mixed with linseed oil. Consequently, the use of chalk as a white pigment in painting experienced a decline for the same reasons. This shift marked a transformative period in the history of artistic materials and techniques.
Understanding the history of pigment production and the various applications of specific pigments is vital in the context of art authentication, not least because of its role in identifying anachronisms in paintings.
