Why are engineering and mechanical drawings blue? These drawings are all blue, depending on how they are drawn. These drawings are not drawn or printed, but "dried". Perhaps in the streets and alleys you can always see some signboards with pictures posted on the door of some printing shops, which refers to this.
Printing paper, commonly known as "blueprint paper", is a kind of chemical coating paper, specially used for printing drawings of various engineering designs and machinery manufacturing. It is an indispensable supply in production, scientific research, and construction.
Blue architectural engineering drawings are a mass drawing method developed in the era before computer drawing.
The draftsman draws the drawing with a carbon pen on a transparent paper called "sulfuric acid paper". The purpose is to facilitate the use of a "printing machine" to print out a large number of identical drawings when a large number of drawings are used in the future.
The blue color on the drawing is caused by the working principle of ammonia fixation and sensitization of the "printing machine" and has no other meaning.
picture
At present, draftsmen can use CAD to complete various structural drawings instead of hand drawing. At the same time, when drawing, they can use a large plotter shaped like a printer to print the drawings in the computer on white drawing paper. Can be printed in color.
However, in order to copy the same drawing in large quantities, designers still use the past "printing method". The drawing cost of this method is very low. The cost of printing an A1-sized drawing into a blueprint is about 0.80 yuan. And it is very efficient. It only takes a few seconds to print an A1-sized drawing into a blueprint.
If you don't want the drawing to be very blue, you can slow down the time it takes to post the drawing; conversely, if you speed up the time it takes to post the drawing, it will become bluer.
Blueprint paper (blueprint yaper) is also called drying paper, and diazo salt is just like drying paper or diazo photosensitive paper. A kind of processed paper made by using blueprint base paper as the paper base, and then coating the dry base paper with photosensitive agent. It is roll paper.
The base paper is required to have good wet tensile strength and absorption properties, minimal wet deformation, and does not contain chemicals that affect the performance of the sensitive material. It is usually made from cotton pulp or bleached wood pulp on a paper machine. Blueprint paper made from qualified base paper has the characteristics of smooth paper surface, uniform photosensitive layer coating, and no white spots, spots, chemical stains, wrinkles, etc.
The usage methods for posting drawings include:
1. Wet method drying drawings, that is, water-washed drawings, also known as iron salt drawings, whose photoreduction is washed with water, and some units still use this method.
2. Dry printing drawings, that is, diazo additive drying drawings, or ammonia fumigation drying drawings. The photosensitive reduction system uses ammonia gas. This kind of drying drawings are supplied in China.
3. There are two types of semi-wet printing methods. One is to apply photosensitizer and reducing agent on the paper, and the photo is combined to form a picture. There is no such method in China; the other is for dry printing, in which ammonia is evaporated during printing. It forms a mist so that it can be photographed while drying.
From the line color, it is divided into:
1. Blue lines on a white background, white lines on a blue background, and brown lines on a white background are wet drying drawings.
2. Purple lines on a blue background, brown lines on a white background, and black lines on a white background are dry-printed drawings. In China, most of them are purple lines with a blue background, and some areas have blue lines or black lines with a white background.
From the coating surface: there are two types: single-sided coating and double-sided coating:
1. Single-sided coating has two meanings: one is to only apply photosensitive liquid on the paper being used; the other is to apply photosensitive agent on one side and boric acid water on the other to eliminate the warpage of the paper and extend the storage period. In fact, they are coated on both sides. Because only one side is photosensitive, they are also called single-sided coated shoes. Most areas in the country are of this type.
2. Double-sided coating means applying photosensitive agent on both sides, and you can print pictures on both sides. This is mainly to reduce the volume of data and save paper. At present, there are 19 places in China that produce printing drawings, including Shanghai, Beijing, Tianjin, Hangzhou, Nanjing, and Wuhan. The development direction in recent years is white background with blue lines and double-sided coating, because the blue line printing drawings will not change during storage time. Below, the photosensitive speed is 1/5 faster than the purple line, and the color is bright, and the photosensitive speed tolerance is large.
