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Papermaking - pulp from plants

  1. Sep 4, 2016 #1

    Stephen Tashi

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    In handmade papermaking, are the chemical treatments ( e.g. boiling in soda ash, soaking bamboo in lime juice) necessarily for turning raw plant material into pulp? Or is the creation of the pulp just a mechanical process of breaking up the material with a "hollander beater" or some other machine?

    For example, the current Wikipedia article on lignin says that the paper used in making newsprint contains most of the original lignin in the plants. Does this imply that chemical treatments to dissolve lignin aren't needed to create pulp, if one is satisfied with producing paper that will yellow?
     
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  3. Sep 4, 2016 #2

    Bystander

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  4. Sep 4, 2016 #3

    jim mcnamara

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    FWIW - yellowing and paper falling apart with age are made worse by reduced washing. Hence more residual acid in the paper. This is why acid free paper is a must for musuem quality work, and why restorers may attempt to remove acid from older valuable documents.
     
  5. Sep 4, 2016 #4

    Fervent Freyja

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    That's right, mechanical pulping is necessary for papermaking, but chemical delignification isn't always necessary for bleaching or brightening the paper. The lignin can be left in the mechanically pulped batch, then chromophores or color-causing molecules can be removed from the lignin with a different chemical treatment (doesn't dissolve the cellulose or lignin), which is more cost-effective as chemical delignification removes more bulk product. Also, some plants like Hemp have little lignin, so no chemicals are needed to make Hemp paper and it doesn't yellow.
     
  6. Sep 4, 2016 #5

    Stephen Tashi

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    The craft-oriented descriptions of making paper by hand say (for many common plants) to boil the plants in soda ash to "remove impurities". It isn't clear to me if this accomplishes delignification or whether "impurities" refers to something else.

    I tried making paper with some amaranthus ("pig weed") that grows in my yard. It was boiled in soda ash and pulped in a blender. The pulp is slightly sticky - unlike pulp I've made from copier paper. It makes a reasonable sheet of paper, but it tends to glue itself to any surface it is drying upon.
     
  7. Sep 4, 2016 #6

    Fervent Freyja

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    It looks to me as if the sodium carbonate is used to increase the pH in order for the dye to take (probably removing waxes or hydrophobic impurities). It isn't breaking the cellulose down, and chemicals that break down lignin also break down cellulose, so, I'm not sure if it is dissolving the lignin.
     
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