Jerry Hamblen, age 11, of Tucson, Ariz., for his question:
HOW IS A BLUEPRINT MADE?
A blueprint is a duplicate or copy of original plans for a building or other construction work. It is made by a photographic process that resembles the way a photographer makes prints of pictures that he has taken.
Blueprints are usually prepared by architects, engineers, designers and draftsmen for the guidance of workmen. A blueprint shows the workman both the size and the location of each piece of material as the project is being assembled or as the building goes up.
In order to make a blueprint, an architect or engineer must first make the original plans or drawings on paper or cloth which allows light to pass through. He makes his drawings with a pencil or India ink.
Blueprint paper is made by applying a solution of two chemicals to any suitable white paper: ferric ammonium citrate and potassium ferricyanide. This solution makes the paper sensitive to light.
A piece of blueprint paper is placed under the original drawing in a printing frame. Then it is exposed to a strong light. The light shines through the paper of the original drawing, but it does not shine through the lines made with pencil or India ink.
When washed in pure water, the blueprint paper turns blue in the places where light has activated the chemicals. But the lines on the original plan do not let light through to the blueprint paper. The lines remain white.
The water washes off the chemical solution so the white lines will not turn blue when exposed to further light. The workman now has an exact copy of the original plans.
Another process is sometimes used to make blueprint paper. This process produces black, blue or red lines on white paper.
By using blueprints, the architect or engineer need make only one set of original drawings.
A worker must be able to understand his copy of the drawing. This is called reading a blueprint and differs from the skill of making the original drawings. In some large scale operations that employ many persons who perform the same job, a supervisor reads the drawings.
Many people are familiar with the architectural blueprints used for homes and other buildings. But probably fewer know about the engineering blueprints needed for mass production in factories. A worker on an assembly line often uses a blueprint of an assembly drawing, which shows how various parts of a machine are to be put together.
Production workers often use blueprints of a detail drawing to show them how to make each part that will be put on an assembly line.
Engineering or technical training is not necessary to be able to read these drawings, for the most part.