Chamfering

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The paper graining is a technique of paper restoration to fill in imperfections (holes, tears) in the paper. By means of an aqueous fiber suspension , similar to paper production , the fiber liquid is flushed over a very fine sieve, whereby the fibers are deposited on the imperfections and on the edge of the paper. They felt together and give the paper new stability and strength, making it usable again.

procedure

The main purpose of the paper grain is mechanical stabilization. Cracks are closed, imperfections are added or paper is laminated locally or over the entire surface. Often the paper is new to its original shape drawn . The damaged sheet (original) is placed on a carrier fleece on a water-permeable material, similar to the papermaker's scoop shape . Before coming into contact with the aqueous treatment solutions, the typefaces should be fixed locally, because the writing materials used, i.e. inks, inks or stamps, are often water-sensitive. The damaged leaf is then moistened by spraying.

The bowl is now flooded with water, and the highly diluted cellulose suspension is added over the damaged leaf . This is now sucked down through the sieve. A sheet that has been placed on it forms an obstacle to the flow of fibers, so that the individual paper fibers can only settle at the points on the screen where no obstacle affects the flow. The missing parts of the sheet and all exposed parts of the screen will be covered with matted fibers, i.e. with new paper.

After the beveling, the very water-containing and very unstable combination of original and sprue must be stabilized. Therefore, the sheet should be lifted out immediately with the help of the carrier fleece and dried. Drying is necessary under pressure. The drying process of freshly fiber leaves usually has the following objectives:

  • Avoidance of tension between old and new leaf areas
  • Preservation of the original textures
  • Equalization of the visual differences between the original and the infusion

The fibrous sheets are stacked and pressed between two polypropylene fleeces and wooden cardboard to dry . The polypropylene nonwovens used have the property of transporting water within their fiber material. This allows different water contents in the pressed material to be standardized. Thanks to the wooden cardboard, the pressure in the stack is reduced to such an extent that the sheets lie flat between the fleeces and are still flexible enough to follow the dimensional changes as drying progresses. In this way, there is no risk of the color and ink layers leveling or changes to the original appearance. The polypropylene fleeces used do not themselves leave any marks or foreign structures, because they are soft, loose and dimensionally stable, only being responsible as a medium for water transport without being able to absorb water themselves.

Chemical processes

The hold between the original and the sprue is created by the overlapping of fibers, which is clearly visible when the edges of the imperfections are smooth (cut edges, worm holes). This cohesion of the paper is mainly due to the hydrogen bond . The use of pressure and increased temperature during the pulping and paper production can intensify the formation of hydrogen bonds.

The strength of the paper, regardless of the nature of the fiber material and without binding agents or sizing processes involved, is guaranteed:

  • due to the matting of the fibers with one another
  • by the adhesion between the fibers
  • through the formation of the fiber-fiber bond

The paper fibrillation of imperfections with fiber suspension usually leads to optically perfect results. The use of identical materials, the guarantee of deacidification and buffering as well as the use of suitable non-volatile preservatives suggest that the fibrous paper will be highly resistant to aging.

Problems with paper fraying

The basic problem of fiberising lies in the difference in the expansion factors of the aged and new fibers. Their combination is only a compromise. As with all wet processes, fiberizing the paper can lead to changes in the format of the paper. Practical experience shows different strengths in the border zones with the current state of paper fiberization. This results in a limited mechanical load capacity. In addition, the hydrogen bridges required for the beveling only form with freshly ground materials and only when the bondable zones come closer together. In the original, however, the fibers are only in an aged form, so to speak keratinized. This state cannot be converted into the necessary binding form, because no process can take place on the original that is comparable to the grinding of the fibers. In the case of old papers, which were produced before the introduction of the Dutchman , this circumstance has an aggravating effect on the renewed formation of hydrogen bonds between the original and the sprue. If wood pulp-like papers are present, the formation of hydrogen bridges is hindered by the lignin coating of the fibers.

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