Author | Zhang Wenjing
The National Library of Ancient Books is located at No. 7 Wenjin Street, Xicheng District, Beijing, adjacent to Beihai Park, and the courtyard is full of antique buildings.
However, after going around to the Wenjin Building, go down the steps from a small door, and you will find a different world.
The rooms are filled with beakers, measuring cylinders, balances, reagents, and a variety of instruments that look like laboratories in scientific institutions.
Few people may know that in a cultural institution such as the National Library, there is also a group of science students who use science and technology as a "weapon" to help precious ancient books resist the invasion of the long years.
After deacidification, the literature can still "live" for at least 300 years
On the desk of the laboratory, there is an old book that has been taken apart.
The book was cut into four parts, some of which were white in color, some yellow, some soft and smooth to the touch, and some rough in texture.
Tian Zhouling, a research librarian at the National Library of China and head of the Document Protection Group of the Ancient Books Library, told China Science Daily that this is an old book of the Republic of China bought by the staff, and four parts are cut for experiments - one part is used as an original for control, one part is used for aging experiments, some are deacidified by technology, and the last part is re-aging experiments after deacidification.
Those whitened papers that are soft and smooth to the touch are the result of deacidification.
In addition to the appearance that can be distinguished at a glance, the staff will also test the physical and chemical indicators of these papers, and observe the changes of the paper after aging and deacidification.
Physical indicators such as whiteness, thickness, tensile strength, tearing degree, bending resistance, etc., and chemical indicators include pH value, alkali reserves, etc.
These experiments involved one of the most important tasks of Tian Zhouling's team – fighting acidification of the literature.
Acidification is the enemy of literature protection. "The main component of paper is cellulose, which is equivalent to the skeleton of paper and is also the main source of paper strength. Under acidic conditions, cellulose hydrolyzes quickly, while under neutral or alkaline conditions, its hydrolysis rate is much slower or basically inhibited, so acidification accelerates the aging of paper. Tian Zhouling explained.
As early as 2004, the National Library completed a survey of the pH of the collections.
The results show that the literature in the National Library of China is seriously acidified, especially the literature in the Republic of China period is the most urgent, and the preservation life is less than 100 years.
"Because traditional Chinese paper is handmade hemp paper made of limestone and other materials and alkali, it has strong acid resistance. In the Republic of China period, handmade paper began to transition to mechanical papermaking, and raw materials also changed from phloem fibers to bamboo pulp and grass pulp. On the one hand, the cellulose content of the raw material itself became lower, and on the other hand, the acidic papermaking process began to be used, which led to the acidification of literature paper in the Republic of China period. Tian Zhouling said.
Combating literature acidification is the research direction that Tian Zhouling has established since the beginning of her work.
In 2005, Tian Zhouling graduated from Beijing Institute of Technology with a master's degree in applied chemistry and entered the National Library.
When she first entered the library, when she visited Ren Jiyu, then the honorary director of the National Library, she heard about the problem of book acidification for the first time and learned about the urgency of deacidification research.
After returning, Tian Zhouling immediately began to search for relevant literature at home and abroad and carry out research on deacidification technology.
For more than ten years, she has published many papers, presided over multiple research projects, and led the team to develop new literature paper deacidification technology.
This technology adopts the anhydrous liquid phase method for deacidification, which can realize whole, batch and integrated deacidification.
These deacidification literature throughout the book have no liquid residue, dry fast, do not deform, and all kinds of handwriting are not affected.
Foreign deacidification equipment is often tens of millions of yuan, and the deacidification price of single-page paper is as high as dozens of yuan. The cost of literature paper deacidification technology developed by Tian Zhouling and her team is less than a quarter of that of foreign countries, and the deacidification efficiency is higher and the safety is stronger.
Today, this technology has been applied in domestic libraries, museums and archives, and will be fully introduced to the market.
Tian Zhouling said that the use of this technology deacidification literature has more than 2,000 volumes and more than 300,000 pages, and the pH value of the paper after deacidification is increased from 3, 4, 5 to 6 and 7, and it can be "lived" for at least 300 years by aging experiments.
Keep bugs in the national map
When Tian Zhouling first entered the National Library, the brain drain of scientific research laboratories was serious, leaving only one old comrade and no equipment available.
After more than ten years of development, the literature protection team led by her has become a professional and mature team of 7 people with tacit understanding.
Deputy Research Librarian Zhang Ming came to work at the National Library of China after graduating from the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences, majoring in applied chemistry.
In addition to participating in the research of deacidification, Zhang Ming is also engaged in research on the durability of handwriting preservation, including pen ink handwriting, printing clay handwriting, etc.
"After hundreds of years of preservation, some of these handwriting materials will fade or even disappear, and some handwriting with more oil content will spread." The research I did was to select a certain handwriting material, artificially accelerate aging under different conditions, and compare the changes before and after. These changes include macroscopic, such as chromatic aberration, ink diffusion, as well as microscopic, such as infrared spectroscopy, changes in chemical composition, and changes in mechanical properties such as friction resistance, and the durability of handwriting materials is studied by analyzing this series of changes. Zhang Ming introduced.
"After comparison, we can see which environmental conditions are sensitive to a certain handwriting material, and it is necessary to avoid the corresponding environmental factors in the preservation process." Zhang Ming said, "We can also further use the existing handwriting material to reverse its chemical composition, and then evaluate its production process in combination with historical materials to lay the foundation for protection." ”
Shanshan Ren, deputy librarian, is one of two biology-trained members of the team, whose work focuses on biological control, which is to monitor and control harmful microorganisms and pests, and to process the literature of mold and mold.
Ren Shanshan and her colleagues are also responsible for a special job - raising insects.
In a light incubator in a laboratory, there were several bottles and cans containing the bugs they raised.
"We have to observe what kind of impact these bugs have on different papers under various temperature and humidity environmental conditions, and then try to use different means to deal with them, so as to find better ways to remove insects." Ren Shanshan said.
Microbial monitoring in the literature warehouse is also an important task for Ren Shanshan. Especially in the summer high temperature and high humidity environment, Ren Shanshan needs to regularly monitor the microbial concentration in the air of the warehouse.
"We put the medium in the warehouse, take active sampling, take the sample and then culture it, then write down how many bacteria grow up, and then convert to know how many microorganisms are in the air." Once the number of microorganisms exceeds the standard, the necessary means must be taken to control it. ”
Ren Shanshan said, "In the absence of mold outbreaks, we will use means such as opening fresh air systems, cooling and humidification; if mold outbreaks occur, we need to do local isolation of the warehouse environment, in addition to basic means such as cooling and humidification, we also need to carry out some mold removal work." ”
Ancient craftsmanship + modern technology
The warehouse management involved in Ren Shanshan's work is also one of the tasks undertaken by Tian Zhouling's entire team.
"Almost all the warehouses in the Museum of Ancient Books are equipped with a temperature and humidity monitoring system, which is in our charge. The monitoring data is transmitted to our office, and we also go to the warehouse every week to ask if there is any problem with temperature and humidity. Once it is found that the temperature and humidity of the warehouse are not suitable, we must find the corresponding personnel to adjust, and different seasons have different requirements. Tian Zhouling introduced.
Every year, Tian Zhouling's team monitors the harmful gases in the warehouse, such as formaldehyde, TVOC (total volatile organic compounds) and so on. The total number of colonies in the storehouse also needs to be monitored every year, especially in the summer.
"The object of our protection is the carrier of literature, and once the carrier does not exist, our culture will suffer great losses, so our responsibility is great, and our scientific research work must solve practical problems." Tian Zhouling said.
Ancient book restoration is an ancient craft. In Tian Zhouling's view, their restoration skills are superb.
"In addition to traditional restoration techniques, if more technology can be added, it can produce better protection effects." The same is the restoration of ancient books, the original we are using tap water, if you add a little protective chemical components to the tap water, you can better extend the life of ancient books, play a better role in protection. ”
"Maybe the outside world doesn't know much, in fact, there is still a lot of scientific research in the library, whether it is a traditional document paper carrier, or a variety of emerging carriers such as compact discs and vinyl records, which need to be protected." In the future, the development and integration of these cultural resources will also require the support of scientific and technological forces in order to be able to develop better. Tian Zhouling said.