The creation of paints during the Renaissance was a complex and labor-intensive process, integral to the operation of the artistic workshop (the bottega). Artists, or more often their apprentices, prepared all the necessary materials themselves, from pigments to binding media.
Raw Materials for Pigments
Pigments, or coloring agents, were sourced from various origins:
• Minerals and Precious Stones:
• Ultramarine (a deep blue) was made by crushing the semi-precious stone lapis lazuli into a very fine powder. It was the most expensive pigment, often reserved for the robes of the Virgin Mary.
• Other minerals like azurite and malachite yielded blue and green shades.
• Various mineral ores and clays were used to obtain ochre (yellows, reds, browns) and green earth.
• Plant-Based Materials:
• Substances from plants like saffron or Brazilwood were used to create lake pigments (organic dyes precipitated onto an inert filler), which provided reds and yellows.
• Indigo yielded blue.
• Animal-Based Materials:
• Carmine (a bright red) was derived from cochineal insects.
• Bone black (black) was made by burning animal bones.
• Artificial Pigments:
• Some colors, such as lead white and lead-tin yellow, were created through complex chemical processes within workshops or by specialized artisans.
• Vermilion (a bright red) – mercuric sulfide – was also produced artificially.
The Manufacturing Process
The process of turning raw materials into usable paint required many steps, often carried out by junior apprentices:
1. Crushing: Raw materials like stones or minerals were meticulously ground in mortars using a pestle. This was a long and strenuous task.
2. Washing and Sieving: The resulting powder was repeatedly washed and sieved to remove impurities and separate particles of the desired size. For ultramarine, this process was especially complex and multi-staged to isolate the pure pigment.
3. Mixing with the Binder (Medium): Once the pigment was ready, it was mixed with a suitable binding agent to create the paint. The choice of medium depended on the painting technique:
• Tempera: Egg yolk was the most common binder used. Tempera-based paints dried quickly and were popular in the Early Renaissance.
• Fresco: Pigments were mixed with water and applied directly onto wet lime plaster, where they became chemically fixed as the plaster dried.
• Oil Painting: In the Northern Renaissance, and later in Italy, drying oils (linseed, walnut, or poppy) became widely used. This binder allowed artists to work longer, create seamless color transitions, and produce layered, detailed images.
4. Fine Grinding: The final mixing of the pigment with the binder often took place on a stone slab using a special grinder (a muller) and required exceptional care to achieve a smooth, uniform paste.
The Role of the Master and Apprentices
While the Master Artist possessed deep knowledge of materials, they rarely performed the routine preparation of paints. This duty fell to the apprentices and students, who thus gained experience and knowledge of each pigment’s properties. Knowing how to create stable and vibrant paints was a trade secret of the workshop and a key element of professional training. The shift to oil painting, which required more mixing of colors on the palette or even on the canvas itself, made Masters more acutely aware of potential incompatibilities between pigments and their behavior in different media.