Deacidification (paper)

from Wikipedia, the free encyclopedia

Under acidification refers to the conservation of paper , various methods for neutralization of acid contents in order so before further advancing paper disintegration save. One speaks of mass deacidification when books or files are deacidified in large quantities. This can also be done automatically .

background

The acids were mostly introduced into the paper as a result of production - almost exclusively from the beginning of industrial paper production in the mid-19th century through the use of pulp . With alkaline active ingredients, however, they can also have entered the paper afterwards through environmental influences. The effects of acids break down cellulose by shortening its macromolecule. This leads to a degradation of the cellulose fibers and an associated reduction in tear resistance. The mechanical strength of the paper decreases and thus leads to irreversible damage to the paper. In the course of time, wood pulp paper in particular forms decay products of the lignin contained in it due to the raw material , which also damage the paper.

As a rule, the acid content of the paper cannot be determined with simple pH value measuring devices , as the paper would have to be moistened for this. Instead, felt-tip pens with appropriate pH indicators are used. The aim of deacidification is to bring the paper into the alkaline range with measured values ​​between pH 7 and 9. A distinction is made between the liquid phase process and the dry process:

  • Liquid phase process, for example the Papersave process or the Book-CP process
  • Dry process, deacidification in the gas phase
  • Aqueous single-sheet process, such as the Vienna process, Bückeburg process

Liquid phase process

In the case of mechanical mass deacidification, only liquid-phase processes are used, e.g. B. in the block deacidification system of the society for the protection of written cultural assets mbH (GSK), developed in cooperation with the University of Applied Sciences Hanover .

In the liquid phase process, the books in wire baskets are immersed in a bath with anhydrous solvent (e.g. hexamethyldisiloxane ) containing ethanolates for several hours . The ethanolates, especially titanium and magnesium ethanolate, neutralize the acid and build up an alkaline reserve in the paper.

In 2016 the University of Graz presented a process in which paper can be automatically deacidified using a liquid enriched with nanoparticles .

Dry process

In the dry process, powder mixtures with alkaline active ingredients, such. B. applied from magnesium oxide and calcium carbonate on the paper.

Advantages of dry processes include low costs and the avoidance of color changes. A disadvantage, however, is that the powder used for deacidification is distributed unevenly on the paper and only the paper surface can be deacidified as a result.

literature

See also

Individual evidence

  1. ↑ Book deacidification deep into the fold.
  2. ↑ Unique in the world: fully automatic washing machine for books. In: Hessische / Niedersächsische Allgemeine . October 1, 2010 at hna.de , accessed on October 8, 2010
  3. ↑ The Preservation of Cultural Property - Projects and Measures of the University Library Braunschweig ( Memento from March 5, 2016 in the Internet Archive ), p. 14
  4. ↑ Andreas Schweiger: The books washing machine. University of Graz, October 5, 2016, accessed on October 7, 2016 .
  5. ↑ JP: Book washing machine. In: VÖBBLOG. October 6, 2016, accessed October 7, 2016 .