The term “blueprint” has long been associated with architectural and engineering drawings, but what exactly is a blueprint, and why is it called that? To understand this, we need to delve into the history and evolution of architectural documentation and the methods used to reproduce detailed plans for construction.
The Origin of Blueprints
The term “blueprint” originates from a specific method of reproducing architectural and engineering drawings that was popularized in the 19th and early 20th centuries. This method, known as the cyanotype process, was developed by Sir John Herschel, a British scientist, in 1842. The cyanotype process involved using a photosensitive solution to create white lines on a blue background, which is how blueprints got their name.
How Blueprints Were Made
The traditional blueprinting process involved several key steps:
- Preparation of the Original Drawing: The original drawing was created on translucent paper or cloth with black ink or pencil. This drawing was known as the “master” or “original” drawing.
- Creating the Blueprint: The master drawing was placed on top of a sheet of paper coated with a photosensitive iron compound. This coated paper was then exposed to ultraviolet light (usually from the sun) through the master drawing. The areas exposed to light would turn a dark blue, while the areas protected by the lines of the drawing remained white.
- Development and Fixing: After exposure, the paper was washed in water to develop the image, which involved removing the unexposed, unreacted chemicals. The final result was a print with white lines on a blue background, which was both durable and readable.
Why “Blueprint”?
The name “blueprint” directly references the distinctive blue color of the finished drawings produced by this process. This term became a standard way to refer to these technical drawings because of their unique appearance and the ease with which they could be reproduced.
The Advantages of Blueprints
The blueprinting process offered several advantages:
- Cost-Effective Reproduction: The process allowed for multiple copies of a drawing to be produced relatively cheaply. This was especially valuable in an era before digital printing and copying technology.
- Durability: Blueprints were relatively durable and could withstand handling and transportation, which was important for construction projects.
- Clarity: The high contrast between the white lines and the blue background made the drawings easy to read and interpret.
Evolution Beyond Blueprints
While the term “blueprint” is still used colloquially, the actual process has largely been replaced by modern reproduction methods. Advances in technology have introduced several alternatives:
- Diazo Copies: In the mid-20th century, the blueprinting process was largely replaced by the diazo process, which produced drawings with a white line on a blue or black background. This method was more versatile and less toxic.
- Digital Printing: Today, most building plans are created and shared in digital formats. CAD (Computer-Aided Design) software allows for detailed and precise drawings, and digital printers produce high-quality copies in various colors and formats.
- Photographic Reproduction: Techniques such as laser printing and high-resolution scanning have replaced older methods, offering even greater accuracy and detail.
Conclusion
The term “blueprint” persists as a piece of architectural and engineering vernacular, even though the actual process of creating these documents has evolved significantly. The name is a nod to the historical methods of producing technical drawings and represents a time when blue was the hallmark of precision and clarity in architectural documentation. Today, while the technology has advanced, the foundational principles of creating and sharing detailed plans remain integral to the construction and design industries.