Paper grain

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As Papieranfaserung refers to a technique of paper restoration to complement defects (holes, torn corners etc.) in the paper. A fiber suspension (paper fibers finely divided in water) is placed on the damaged sheet of paper lying on a fine sieve . The water is withdrawn downwards through the sieve, the paper fibers collect on the sieve in the area of ​​the imperfections and sheet edges. The fibers become matted with one another and, similar to paper production, form new paper where the original paper is missing. Thus they give the paper new stability and strength, making it usable again.

Process of paper graining

There are a large number of devices and machines for fibering, from self-made chamfering boxes to professional devices for individual fibering to the Fourdrinier fiberizing machine, where the sheets are guided through the fiberizing unit on a transport screen. However, the basic principle of beveling is always the same.

The damaged sheet 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, it must be checked whether the writing materials used, i.e. inks, inks or stamps, are water-sensitive and must first be fixed. The damaged blade must be thoroughly moistened before the beveling.

The scoop shape is now flooded with water, and the highly diluted fiber suspension is added over the damaged leaf. Then the water is let out of the ladle and sucked down through the sieve. The paper fibers are retained on the carrier fleece. A sheet that is placed on top of it forms an obstacle in the flow of fibers, so that the individual paper fibers can only settle at those points on the carrier fleece where no obstacle affects the flow. The missing parts of the sheet and all exposed parts of the screen are covered with matted fibers, i.e. with new paper, but the remaining parts of the sheet are not, except for an approximately 1 mm wide overlap.

After the beveling, the very water-containing and very unstable combination of original and sprue must be stabilized. The sheet is therefore immediately lifted out with the aid of the carrier fleece and dried. Drying is usually done 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 surface structure of the paper
  • Equalization of the visual differences between the original and the infusion

Processes in the paper during bevelling

The hold between the original and the bevelling is created by the overlapping of fibers, which is clearly visible when the edges of the imperfections are smooth (cut edges, wormholes). 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

Additional stabilization can be used, for. This can be achieved , for example, by re-gluing or by applying thin silk or Japanese paper on one or both sides directly after the bevelling. This is particularly common with papers that have a low mechanical strength due to numerous cracks, large defects, degradation by microorganisms or the like.

Paper fray problems

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 be carried out 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 the paper contains wood pulp , the formation of hydrogen bonds is hindered by the lignin coating of the fibers.

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