Prussian blue (also known as Berlin blue) is a synthetic, deep blue pigment invented in Berlin around 1706. It was the first modern synthetic pigment and is recognised by its intense, dark blue colour. In the construction world, Prussian blue has served various purposes over the centuries, from decorative paint finishes to technical markings on building sites.
Chemically, Prussian blue is iron hexacyanoferrate, a complex compound of iron and cyanide. The pigment is lightfast, relatively inexpensive, and has excellent covering power, which made it attractive for large-scale applications in building and construction. The colour is so distinctive that “Prussian blue” has become a standard colour name in many languages around the world.
Applications
Prussian blue has been used across the construction and related industries in several ways:
- Decorative paints and coatings — Historically widely used as a pigment in exterior paints, particularly on woodwork, shutters, and facade elements. The colour was especially popular in the 18th and 19th centuries.
- Marking paint — On construction sites, blue pigment is used to apply markings on concrete, steel, and timber. Prussian blue was long the standard pigment for this purpose.
- Heritage restoration — During the restoration of historic buildings, Prussian blue is still occasionally used to recreate original colour schemes with period-accurate materials.
- Blueprints — The pigment formed the basis of the cyanotype process, the famous “blueprint” method that was the industry standard for copying construction drawings for decades.
- Limewash and silicate paint — As an additive in traditional limewash mixtures for facades and interiors of historic properties.
Today, Prussian blue has been largely replaced in many applications by more modern synthetic pigments such as phthalo blue, which offer even better lightfastness and chemical stability. However, Prussian blue remains relevant in restoration work and specific decorative applications where historical authenticity is required.
Related terms
- Pigment
- Limewash
- Blueprint
- Coating
- Restoration
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.