Why are all engineering drawings blue?

Printing drawings, commonly known as "blue drawings", is a kind of chemical coating processing paper, which is specially used for various engineering design and mechanical manufacturing printing drawings. It is an indispensable product in production, scientific research, and construction.

The blue architectural engineering drawing is a mass drawing method formed in the era when there was no computer drawing.

The draftsman used a carbon pen to draw the picture on a transparent paper called "sulfuric acid paper". The purpose is to facilitate the use of "printing machine" to print a large number of identical drawings when a large number of drawings are used in the future.

The blue on the drawing is based on the working principle of the "printing machine" ammonia fixing photosensitive, and has no other meaning.

At present, draftsmen can use CAD to complete the drawing of various structural drawings without drawing by hand. At the same time, when the drawings are produced, they can use a large plotter like a printer to print the drawings in the computer on a white drawing. Can be printed in color.

However, in order to copy a large number of the same drawing, the designer is still using this "printing method" of the past. The drawing cost of this method is very low. The cost of printing an A1 size drawing into a blueprint is about 0.80 yuan. And the efficiency is very high. It only takes a few seconds to print an A1 size drawing into a blueprint.

If you don’t want the drawing to be very blue, you can slow down the printing time; on the contrary, if the printing time is faster, it will be bluer.

Printer

Blueprint (blueprint yaper) is also called blueprint, diazonium salt is like blueprint or diazo photosensitive paper. A processed paper made by using blueprint base paper as the paper base, and then coating dry base paper with a photosensitive agent, is a rolled paper.

The base paper is required to have good wet tensile strength and absorption properties, very small wet deformation, and does not contain chemicals that affect the properties of sensitive materials. It is usually made of cotton pulp or bleached wood pulp on a paper machine. The blue paper made of qualified base paper has the characteristics of smooth paper surface, uniform coating of photosensitive layer, no white spots, spots, stains, wrinkles, etc.

From the method of use, the printed drawings are divided into:

1. Wet drying drawings, that is, washing drawings, that is, iron salt drawings, the photosensitive reduction system is washed with water, and some units still use this method.

2. Dry drawing, that is, diazo-addition drawing, or ammonia fumigation drawing. The photosensitive reduction system uses ammonia gas. This kind of drawing is supplied domestically.

3. There are two types of semi-wet printing drawings. One is to apply both sensitizer and reducing agent on paper, while the photosensitive is coupled to form a picture, which is not available in China; the other is for dry printing, which evaporates ammonia when printing. Fogging, make it into a picture while drying.

From the color of the line, there are:

1. Blue lines on a white background, white lines on a blue background, brown lines on a white background, and wet drawings.

2. Blue bottom purple line, white bottom brown line, white bottom black line, dry drawing. At present, most of the domestic lines are blue and purple lines, and some areas have white or black lines.

Divided from the coating surface: There are two types of single-sided coating and double-sided coating:

1. Single-sided coating has two meanings: one is to coat only the photosensitive liquid on the used paper; the other is to coat one side with a photosensitive agent and the other side with boric acid water to eliminate the warpage of the paper and increase the storage period. In fact, it is coated on both sides. Because only one side is photosensitive, it is customarily called single-sided coated shoes. This type of shoe is used in most parts of the country.

2. Double-sided coating means that both sides are coated with photosensitive agent, and both sides can be printed, mainly to reduce the volume of data and save paper. At present, there are 19 places in China, including Shanghai, Beijing, Tianjin, Hangzhou, Nanjing, Wuhan, etc. that produce blueprints. In recent years, the direction of development is blue lines on a white background and double-sided coating, because blueprints remain unchanged for the preservation time. The sensitivity speed is 1/5 faster than the purple line, and the color is bright, and the sensitivity speed has a large tolerance.