Someone always asks, why are engineering drawings and mechanical drawings blue? Everyone probably knows that the word blueprint comes from this. In fact, the reason why these drawings are blue is because of their drawing methods. These drawings were not drawn or printed, but "dried". Perhaps in the streets and alleys, you can always see signs such as printing pictures pasted on the entrance of some printing houses, and this is what they refer to.
Printing paper, commonly known as "blueprint paper", is a kind of chemical coating processing paper, which is specially used for various engineering design and mechanical manufacturing printing, and is an indispensable product in production, scientific research and construction.
The blue architectural engineering drawing is a method of mass drawing formed in the era without computer graphics.
The draftsman draws the picture with a carbon pen on a transparent paper called "sulfuric acid paper". The purpose is to facilitate the printing of a large number of identical drawings with the "printing machine" when a large number of drawings are used in the future.
The blue color on the drawing is due to the working principle of the "printing machine" ammonia water fixation and photosensitive, and has no other meaning.
At present, drafters hardly see hand-painted ones, and all use CAD to complete the drawing of various structural drawings. It can also be printed in color.
However, in order to copy a large number of the same drawing, designers are still using the past "printing method". The drawing cost of this method is very low, and the cost of printing an A1-sized drawing into a blueprint is not high. And the efficiency is very high. It only takes a few seconds to print an A1-sized drawing into a blueprint.
If you don’t want the drawings to be very blue, you can slow down the printing time; otherwise, the faster the printing time, the bluer it will be.
Blueprint paper (blueprint yaper) is also called printing paper, and diazonium salt is just like printing paper or diazo photosensitive paper. It is 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, which is roll paper.
Base paper is required to have good wet tensile strength and absorption properties, minimal wet deformation, and does not contain chemicals that affect the properties of the sensory material. It is usually made of cotton pulp or bleached wood pulp on a paper machine. The blueprint paper made of qualified base paper has the characteristics of smooth paper surface, uniform coating of photosensitive layer, no white spots, spots, medicine stains, wrinkles and so on.
Printing drawings are divided into methods of use:
1. Wet printing, that is, washing and drying drawings, that is, iron salt drawings, the photoreduction system is washed with water, and some units still use this method.
2. Dry printing, that is, printing by adding diazo, or called ammonia fumigation. Its photoreduction system uses ammonia gas, and most of the previous supplies on the market were this kind of printing.
3. There are two types of semi-wet printing, one is to apply both the sensitizer and the reducing agent on the paper, and couple it to form a picture while being sensitive; the other is used for dry printing, and the ammonia water is evaporated into a fog when printing. Make it into a picture while drying.
In terms of line color, there are:
1. Blue lines on a white background, white lines on a blue background, and brown lines on a white background are wet-printed 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. There are mostly purple lines on a blue background on the market, and some areas have blue or black lines on a white background.
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 apply photosensitive liquid only on the paper used; the other is to apply photosensitive agent on one side and boric acid water on the other side to eliminate warping of paper and increase storage period. In fact, it is coated on both sides. Because only one side is photosensitive, it is also called single-sided coated shoes, which is the case in most areas.
2. Double-sided coating means that both sides are coated with photosensitive agent, and pictures can be printed on both sides, mainly to reduce the volume of materials and save paper. In the past ten years, the development direction is blue line on white background and double-sided coating, because the photosensitive speed of the blue line is 1/5 faster than that of the purple line when the storage time remains unchanged, and the color is bright, and the photosensitive speed is tolerant. The degree is large.
