Bleu d'Outremer, also known as Ultramarine Blue, is a deep blue pigment with a rich history, initially derived from the semi-precious stone lapis lazuli. Today, it's primarily a synthetic pigment, prized for its vibrant color and versatility in various applications. It can pull towards purple when used with transparent binders and is known for its excellent UV stability when dry, though it can fade in wet lime-based media.
Here's a more detailed breakdown:
1. Natural vs. Synthetic:
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Natural Ultramarine:
Traditionally made by grinding and processing lapis lazuli, a process that was labor-intensive and costly.
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Synthetic Ultramarine:
Developed in the 19th century as a more affordable and readily available alternative to the natural pigment.
2. Properties:
- Color: A bright, deep blue that can appear slightly purplish with certain binders.
- Transparency: Can be very transparent when used with walnut oil, as in some fine art paints.
- Stability: UV stable when dry, but can be unstable in wet lime-based media.
- Versatility: Suitable for a wide range of applications including lime paint, plaster, fresco, glaze, cement, and cosmetics.
- Chemical Composition: Typically a sodium aluminosilicate polysulphide.
3. Applications:
- Fine Arts: Used in painting (oils, watercolors, etc.), plaster, fresco, and glazes.
- Decorative Arts: Used in lime paint, cement, and other decorative applications.
- Cosmetics: Used in a variety of cosmetic products.
- Other: Can also be found in plastics and rubber.
4. Historical Significance:
- Lapis lazuli, the source of natural ultramarine, was a valuable commodity traded over long distances.
- The development of synthetic ultramarine made the vibrant blue color more accessible to artists and other industries.
- In some contexts, it's referred to as "French Ultramarine" due to its association with the pigment's development in France.