Why do the pages turn yellow after a book stays for a long time?

Generally, the yellowing of book paper is due to oxidation. If you can avoid oxidation as much as possible, you can also avoid the yellowing of the paper.

As long as you can ensure the following three points, the yellowing of the paper can basically be avoided.

These three points are to reduce contact with air, reduce contact with moisture, and reduce contact with sunlight.

Generally, the storage period of paper should not exceed one year, even if the condition of storing the paper is good, the paper will be discolored and deteriorated if it is stored for too long. If the paper is stored for two years, the coated paper will turn yellow and depowder; newsprint turns yellow and brittle; Discoloration and reduced strength of the wrapping paper; Yellow cardboard and containerboard can become moldy and deteriorate, and so on.

In addition to the aging of the paper itself, the destruction of paper fibers caused by oxidation, the addition of chemicals to a large number of modern machines to make paper is also easy to make the paper acidic, and the poor environment (such as air pollution, ultraviolet rays, temperature and humidity, etc.) and man-made damage and other factors will be the factors that cause the deterioration of paper.

White paper is made from the fibers of trees, and because these fibers have a yellowish tint, paper mills use chemicals such as sulfites to bleach. However, when the paper is exposed to the air for a long time, the bleached fibers will oxidize and return to their original appearance, so the white paper will become slightly yellow after a long time! If you want to avoid the paper from turning yellow, it seems that the only way to put the paper in a vacuum environment is to put the paper in a vacuum!

In addition, the paper will turn yellow because the paper contains lignin, which is an acidic substance, which will oxidize the paper due to contact with air, light and environmental moisture, and eventually become brittle and damaged. The paper will turn yellow because the paper contains lignin, which is an acidic substance, which will oxidize the paper due to contact with air, light exposure and environmental moisture, and eventually become brittle and damaged. <>

Because the paper is in Africa.

Cellulose components or harmful substances such as acid and alkali and bleaching powder remaining in the paper will cause the aging of the paper and the corrosion of the paper fibers under the influence of high temperature and high humidity. In addition, dampness can also cause mold and insect damage to books. Therefore, the bookshelves and bookcases of the family should be placed in a dry and ventilated place.

All kinds of light are harmful to books, especially daylight. Therefore, the bookshelves should be protected from direct sunlight. For books that have been damp and waterlogged, the method of ventilation and drying should be adopted, and they must not be exposed to sunlight to prevent the writing from turning yellow and brittle.

Books should be protected from insects. Bookshelves and bookcases can be placed with some sanitary balls wrapped in paper.

Natural camphor. Sperm mass, camphor powder and other harmless insect drugs; In addition, books should be frequently overturned, and books and periodicals that are eaten by insects and rats should be dealt with in a timely manner to prevent the spread. When the books are placed, hardcover books and paperback books can be placed with the spine facing outwards for easy finding.

When placed, if the layer is not full, you can put a book file to avoid the book being loose and crooked, causing the back of the book to be bent and the pages to be curled. Wire-bound books are lighter and should not be placed directly. <>

Don't read in strong light, in addition don't read in rainy and humid weather, one is to make the book moldy, two to accelerate the oxidation process, it is best to wear gloves, because there are a lot of sweat stains and grease on people's hands, these things will be stained on the book with the process of turning the book, the longer the accumulation, the more it will speed up the oxidation process, (these things will make the book yellow) some precious books, it is best to read less, if possible, you can put it in a well-sealed box, put the desiccant, In the case of injecting high-purity nitrogen into the box to prevent oxidation, the paper will be harmed by oxygen and harmful gases in the air under natural environmental conditions, and oxidation and acidification hydrolysis reactions will occur, making the paper yellow and brittle, and the paper can be protected by nitrogen to prevent these reactions. <>

Generally, the yellowing of book paper is due to oxidation. If you can avoid oxidation as much as possible, you can also avoid the yellowing of the paper. Books tend to turn yellow after a long time, and the paper is mainly made of wood.

Because the paper contains wood fibers, most of these natural wood fibers have a faint yellow color. To remove this yellow, white paper is made.

In modern times, sulfur dioxide, which is unstable, is generally added to pulp. Sulphur dioxide has a bleaching effect and can chemically react with colored substances in the pulp to form another colorless, unstable compound. At this time, the color of the pulp will turn white.

As the paper is left for a long time, the colorless compounds will slowly be oxidized and decomposed, and at this time, the paper will turn yellow again.

There are several issues that need to be taken care of

1. The room should be cleaned frequently, and there should not be too many sundries, otherwise, cockroaches will breed, and the book will also be dirty and damaged, which will be annoying.

2. I am used to using bookshelves, and it is easy to access books. If you like to be tidy, it is advisable to use a bookcase, which can greatly reduce the dust on the book.

3. If you do all this, and live in a building, you can keep the books dry, and you can avoid drying the books.

4. The wardrobe also needs to be insect and moisture-proof, and the practice is the same as the above.

5. Appropriate use of mothballs and other deworming methods.

1. The yellowing of the book after a long time is due to oxidation. Paper is made of tree fibers, these fibers will be slightly yellow, paper factories will use sulfites and other chemicals to bleach, if the paper is exposed to the air for a long time, the bleached fibers will oxidize, return to the original appearance, generally speaking, the yellowing of the book does not affect reading.

2. In addition to the destruction of paper fibers caused by paper oxidation and its own aging, modern machines will add chemicals to make the paper acidic when manufacturing paper in large quantities, and some factors such as bad environment and man-made damage are the factors that cause the deterioration of paper.

3. The storage period of general paper will not exceed more than one year, even if the storage conditions of the paper are good, the paper will deteriorate and change color if it is stored for too long. For example, after two years of paper storage, the paper will appear yellowing and depowdering; Wrapping paper is weakened, discolored, and so on.

4. If you want to avoid the yellowing of the paper, you need to reduce the contact with the air, reduce the contact with moisture and reduce the contact with the sun. Contact with air is unavoidable, but contact with moisture and sunlight can be avoided as much as possible. If you don't use some books often, you can put them in a plastic bag and seal them so that you can take them out when you're ready to use them.

Because the main components of the book are hemicellulose and cellulose, which will oxidize with oxygen in the sun, and it will turn yellow at this time.

Because it reacts with the oxygen in the air and is gradually oxidized, the book will turn yellow and brittle after a long time.

Books that have been left out for a long time look dirty because the book has oxidized with the air and some subtle dirt has seeped into the paper.

White paper is a forest mill obtained by adding bleach to the yellow pulp, the bleach will gradually oxidize with oxygen in contact with air and slowly decompose it, after a long enough time, the bleach is completely decomposed, and the paper will change back to its original color - yellow. In addition, the acidic substances in the air will also corrode and damage the paper, accelerating the rate of yellowing of the paper.

Some old books will have yellowed pages, what is the reason for this?

When papermaking workers make paper, the raw materials are crushed and boiled to obtain a yellow pulp, and then people add bleach with bleaching effect to it, so there is white paper. After this bleach comes into contact with the air, it will gradually oxidize with the oxygen and be decomposed little by little, and after a long enough time, the bleach will be completely decomposed and the paper will change back to its original color - yellow.

In addition, the acids in the air can also corrode the paper, which will speed up the rate at which the paper turns yellow.

01 Paper is usually made of wood, and the main components of natural wood are cellulose and lignin. However, lignin and some cellulose are very susceptible to oxidation – they absorb additional oxygen molecules, causing changes in the original molecular structure, especially breaking the bonds in lignin that hold the molecular units together, and forming a molecular region called a "penny chromophore". After the lignin is oxidized, we will see yellow or brown.

Paper is widely used in books, magazines, calligraphy and paintings, stamps, banknotes, contracts, treaties, etc., and is one of the important carriers of recording and disseminating culture, which is closely related to people's lives. However, when you look at the books you used a few years ago, you will be surprised to find that all the paper of the books has turned yellow, and some of the papers have even become "weak", and they will be damaged after a few more turns.

When the finished paper reaches the user, it must go through the processes of cooking, bleaching, dechlorination, whitening, copying, storage in the warehouse, transportation and store display. The raw material of paper is wood, and wood contains a certain percentage of lignin. Lignin is composed of phenylpropane building blocks, and when bleached, lignin remains in the fibers although it becomes a colorless alkylphenol state due to oxidation and hydrolysis, and these alkylphenols become quinone structures through oxidation such as sunlight exposure, which has the ability to absorb visible light and exhibit hues from yellow to brown.

Of course, the yellowing of the paper is also inseparable from the exposure of light, and the yellowing rate of the paper will be accelerated under the exposure to the sun. Certain substances in the air will form strong oxidants under ultraviolet irradiation, which will oxidize and degrade cellulose, hemicellulose and lignin, and cause the paper to age. In addition, ultraviolet light can directly cause the cleavage of C-C and C-O bonds, resulting in a decrease in the polymerization of cellulose, hemicellulose and lignin.

At the same time, the infrared rays in the light will heat the paper, so that the temperature of the paper will increase, the internal reaction speed will be accelerated, and the phenomenon of yellowing, brittleness, and degradation of the edge part of the paper will be accelerated. The yellowing and brittleness of paper is very detrimental to the preservation of books and important documents. Studies have shown that to inhibit the yellowing of paper, lignin must first be removed during the papermaking process.

In fact, as long as some chemicals are added when crushing wood, the lignin can be removed, so as to make paper that is not easy to yellow. However, a quarter of the wood is wasted in this way to make paper. In addition, researchers have also experimentally compared various methods to prevent yellowing of paper, and found that a substance called polyethylene glycol is effective in inhibiting yellowing.

Newspapers coated with polyethylene glycol do not turn yellow even after prolonged exposure to light. Applying different amounts of polyethylene glycol to thick, unprinted newsprint, and then irradiating it with an extra strong artificial light equivalent to two days of direct sunlight, the results showed that the more polyethylene glycol was coated, the lower the degree of yellowing.

The causes of yellowing of paper are complex, considering the raw material composition of the paper and its surrounding environmental influence, it is best to store the collected books and newspapers in a dry and dark place.