Blueprint

A blueprint is a special drawing.

It shows how to build things.

Long ago, people used a special way to make copies. They put a drawing on paper. Then they put it in the sun.

The sun makes the paper turn dark blue. The ink on the drawing stays white. This makes white lines on a blue background.

This was a fast way to make many copies. It cost much less than drawing by hand.

Today, we use computers for most plans. We can see them on screens. These new plans help us build big things.

A blueprint is a copy of a technical drawing.

It shows plans for building things. For a long time, people used a way called the cyanotype process.

This process makes white lines on a blue background.

To make a copy, workers used special paper. They put a chemical solution on the paper first. Then, they put a drawing on top. They clamped everything under glass in a frame. They took the frame into the sun. The light makes the coating change. Where light hits the paper, it turns dark blue. Where the ink blocks the light, the paper stays light. Finally, they wash the paper in water. This washes away the extra chemicals. This way was much cheaper than drawing by hand.

Today, blueprints are mostly digital. Most people use computers to make plans. They can see these plans on screens or tablets. This is called computer-aided design. Many old buildings still use paper blueprints. These old papers help people fix roads and bridges.

A blueprint is a copy of a technical drawing.

These drawings show plans for building things like roads or houses. For a long time, people used a special way to make them. This way is called the cyanotype process. It creates white lines on a dark blue background. This look is actually a negative of the original drawing.

Because they were easy to make, they were very useful. Engineers and architects used them for over one hundred years.

To make a blueprint, workers follow a few steps. First, they soak paper in a special chemical solution. This solution uses things called ammonium ferric citrate and potassium ferricyanide. Next, they place a tracing of a drawing on top. They clamp the paper and the drawing under glass. Then, they put the frame in the bright sun. The sunlight causes a photoreaction in the coating. Where light passes through, the paper turns a deep blue. Where the ink blocks the light, the lines stay white.

Sir John Herschel introduced this contact print process in 1842. Before this, making copies was a very hard job. It could be expensive to trace every drawing by hand. By the late 1890s, blueprints cost much less. In American offices, they cost only one-tenth of hand-traced copies.

This made it much easier for many people to work. It changed how builders and designers shared their ideas.

Many different materials have been used for these prints. Most people used paper for their blueprints. Some used linen to make them more durable. However, linen prints would sometimes shrink over time. To fix this, people used imitation vellum or polyester film. In the 1940s, a new way called diazo printing became popular.

These were called whiteprints because they had blue lines on white paper. Later, large xerographic machines replaced these older methods in 1975.

Today, most plans are digital instead of on paper. This is often called computer-aided design. Workers can view these plans on a computer screen. They can even use smartphones or tablets to see them.

This allows crews to edit and share files in real-time. However, many old paper blueprints are still very important. Most buildings and roads built before 1990 only have paper copies. These help people repair old bridges, sewers, and railroads.

A blueprint is a reproduction of a technical or engineering drawing.

It uses a contact print process to create copies of original plans. This process was introduced by Sir John Herschel in 1842. For over a century, these prints were vital for construction and industry. They allowed for the rapid and accurate production of many copies. This was much more efficient than older methods of reproduction. Today, the term is often used informally to describe any floor plan.

The traditional look of a blueprint is a result of the cyanotype process. This process creates a negative of the original drawing. It features white lines set against a dark blue background. The mechanism relies on a photosensitive ferric compound. The most common version uses ammonium ferric citrate and potassium ferricyanide. To begin, the paper is impregnated with a solution of ammonium ferric citrate and then dried. When light hits the paper, a photoreaction occurs. This reaction turns trivalent ferric iron into divalent ferrous iron.

To create the image, the paper is developed with potassium ferricyanide. This forms an insoluble substance called ferroferricyanide. This substance is also known as Prussian blue or Turnbull's blue. The process requires a specific sequence of steps. First, engineers draw designs on cartridge paper. These are traced onto tracing paper using India ink. The tracing paper is placed over the sensitized paper. Both sheets are clamped under glass in a daylight exposure frame. This frame acts much like a picture frame.

Exposure to light is the next critical step in the sequence. The frame is placed in bright sunlight for one or two minutes. If the sky is overcast, it may take about thirty minutes. Ultra-violet light passes through the transparent parts of the tracing paper. This light causes the coating to convert into a stable blue or black dye. However, the India ink blocks the ultra-violet light. In those areas, the coating does not convert and remains soluble. Once a strong image appears, the frame is brought indoors. The excess, unconverted coating is then washed away and the paper is dried.

Different materials have been used as the base for these prints. Paper was the most common choice for blueprints. For more durability, some workers used linen. However, linen prints had a tendency to shrink slightly over time. To solve this, printers used imitation vellum or polyester film, also known as Mylar.

The introduction of this process changed the economics of design. By the late 1890s, blueprints were much cheaper than manual methods. In American architectural offices, they cost only one-tenth of a hand-traced reproduction.

As technology advanced, the cyanotype process became obsolete. In the early 1940s, it was replaced by the diazo-based whiteprint process. These diazo prints are also called blue-lines or bluelines. They produce blue lines on a white background instead of white lines on blue.

Later, xerographic print processes became the standard. Xerography uses toner on copy paper. Large-format xerographic machines arrived in 1975 and replaced older printing methods. Now, most design work uses computer-aided design, or CAD. This allows designs to be printed directly by a computer printer or a plotter.

In modern engineering, paper is often avoided entirely. The finished design exists as an image on a computer display. For machining parts, the computer generates a computer numerical control sequence. This file controls the tools used to make the part. In construction, workers can view digital plans on smartphones or tablets. Software allows these crews to edit and share documents in real-time. Despite this, original paper blueprints remain very important. Most buildings and roads built before 1990 only have paper copies. These are essential for repairing bridges, sewers, and railroads. They are also used in legal matters to determine property boundaries.