What is the picture in which all the papers are blue?

People always ask, why are engineering drawings and mechanical drawings blue? Everyone may know that the word blueprint comes from this. In fact, these pictures are all blue, because they are related to their painting methods.

These drawings are not drawn or printed, but "dried". Perhaps you can always see some printed products and other brands posted at the entrance of the printing house in the streets and lanes, which is what this means.

Blueprint, commonly known as "blue-blue drawing", is a kind of chemical paint processing paper, which is specially used in various engineering design and machinery manufacturing, and is an essential product in production, scientific research and construction.

Blue architectural engineering drawing is a popular drawing method formed in the era when there was no computer drawing.

The draftsman drew the picture with a carbon pen on transparent paper called "sulfuric acid paper". The purpose is to facilitate the use of "blueprint machine" to make a large number of the same drawings when a large number of drawings are used in the future.

The blue color on the picture is caused by the working principle of ammonia fixing solution and photosensitive of "blueprint machine", which has no other significance.

At present, draftsmen can hardly see hand-drawn drawings, and all kinds of structural drawings are drawn by CAD. At the same time, when drawing, you can use a large plotter shaped like a printer to print the drawings in the computer on white drawings or color drawings.