Paper

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Paper
Dr. Linda M. Perry

First writing surfaces

Animal skins
- Parchment--sheep, goatskins
- Vellum--calf skins. Finer quality than parchment.
- Long-lasting

Paper

Paper--A matted web of cellulose fibers.
- Almost any organic matter with fibrous structure.
- First developed in Egypt, 2500 B.C.
  - Papyrus cross-laid and pounded with a stone.
Modern papermaking
- Method first developed in China, first century A.D.
- Mulberry tree inner bark

Paper Making

Paper Sources

Rag or cotton pulp
- Almost pure cellulose
- Strong durable
Reclaimed pulp (recycled paper)
- Paper submitted to alkali solution to dissolve ink. Chemically reduced to pulp.
Grasses, straw, bamboo, jute.
Mechanical wood pulp
- for newspaper stock.
Chemical wood pulp
- Acids or alkali remove gums, resins.
- Long-, variable- and short-fibered pulps determine paper strength and durability, bulk, opacity and smoothness.

Papermaking (wood)

Digester
- Cleans wood chips by chemicals, temperature.
- Bleached with chloride of lime.
Beater
- Frays walls and ends of fibers.
  - Beaten in water so they mesh and "felt."
- While in beater, materials added to pulp
  - Sizing--Reduces moisture penetration, prevents fuzzing, gives hardness to paper (like starch).
    - Blotting paper is unsized;
    - Newsprint is slack-sized for fast ink-penetration;
    - Writing, litho and offset stock are hard-sized to bind fibers and prevent absorption.

Jordan--Pulp with additives beat again to reduce fibers to more uniform length.

Papermaking machine

Fourdrinier section
- Treated "stock" or pulp:
  - 1% pulp, 99% water.
  - Forced through tiny straining slots onto finely woven wire mesh.
- Wire mesh is a moving, endless screen, constantly vibrating.
  - Interweaves, mats fibers.
  - Fibers tend to flow lengthwise.
    - Directional tendency is grain.
    - Paper tears, folds most easily with the grain.

Dandy roll applies first surface pressure to top of paper. Used for watermarking.
- Watermark: A distinctive design; usually imprint of manufacturer’s name.
  - Becomes an integral part of paper.
  - Design formed with wire and attached to dandy roll, which impresses it into the wet paper.

The paper is formed into continuous roll, or web.

webs

From the presses, the paper moves unsupported to the drying section.
Last step is calendering
Calendering--Stack of 5 to 9 rollers incorporated into the dry end.
- For ironing and smoothing.
- Adds to gloss of finish.
- All paper known as machine-finished (wood paper)

Out of machine

Supercalendering
- Extra step outside papermaking machine
- Used for magazines and booklets.
- Finished by stack of calender rolls.
Coated stock
- (art paper)
- Smooth, shiny or mat finish.
- Web passes through vat with coating mixture.
  - Coating emulsion adheres to paper.
  - White china clay mixed with other agents.
- Gloss produced by supercalendering.
- Retains more ink on surface.
  - More brilliant, denser color, so best for color pictures.

Definitions

Ream--500 sheets
Basis size--Standard size of given paper grade.
- The size in which paper is normally and most conveniently produced.
Basis weight--Weight of ream in basis size.
- 500 sheets of 25" x 38" at 70 lbs. = basis 70
  - (63.5 cm x 203.2 cm at 31.75k, or 105.35 grams per square meter [gsm])
    - Individual sheet is 70-lb. stock, or substance 70
Caliper thickness--Heavy stock, measured with micrometer.

Major Classifications:

Book stock--25" x 38" (63.5 cm x 203.2 cm)
- From 45 to 120 lb. (20.41 to 54.43 k)
Writing stock--17" x 22" (43.18 cm x 55.88 cm)
- Bond papers from 9 to 24 lb. (4 k to 10,89 k)
- Ledger papers from 24 to 40 lb. (10,89 k to 18.14 k)
  - (90 to 150 gsm)
- Manifold (onion skin) 9 lb. (4k)
Cover stock--20" x 26" (50.8 cm x 66 cm)
- 50 and 80 lb. (22.68 k to 36.29 k )
  - 135.5 to 218.22 gsm)
- Heavier is measured in caliper thickness.
International conversions for equivalent weights at http://www.paper-paper.com/weight.html.

Singapore conventions:
Thin paper, 70-110 gsm (writing stock)
Thick paper, 120-160 gsm (writing to cover stock)
Super thick, 170-260 gsm (cover to caliper thickness)
A5 128 gsm art paper (book stock, coated, glossy)
A5 157 gsm art paper (cover stock, coated, glossy)
A4 and A3, 128 gsm art paper (book stock, coated, glossy)
A4 and A3, 157 gsm art paper (cover stock, coated, glossy)

Book Stocks

Antique finish--Similar to early printing.
- Machine finished.
- Eggshell Antique--Rough
  - Finished with special felts
- Text--High grade antique.
  - Quality books, brochures
- Vellum finish--Smoothest grade of antique.
  - Paper vellum--Made from high quality rags for fine book editions and documents.
  - Japan--Mulberry bark imitating classic vellum.
Offset Stock--Smooth, uncoated book stock.
- Generally with a text or vellum finish.
- Sized on both sides to prevent curling.
English finish (EF)--Nonglare, slightly roughened surface.
- Further development of machine finishing.
- Calendered or may be supercalendered.
Coated stock (art paper)
- Ranges from enamel (super glossy) to dull (smooth, but without gloss).
- Matte-coated paper reproduces halftones well due to nonglare surface.

Writing Stocks

Flat stock, bond stock, business paper, ledger stock, onion skin, carbonless paper.

Cover Stocks

Heavier, stronger, easier folding, wider variety of colors.
Finishes: antique, coated, embossed, metallic laid or woven (impressed with pattern of the wire and/or dandy roll.)
- Pebble or ripple--surface pattern applied by rollers

Other paper stocks

Bristol bond--Heavy, stiff printing paper
- Postcards, display cards, brochures.
- Plain bristol, index bristol, coated bristol.
Parchment paper--Waterproofed, extremely high grade of bond paper.
India or Bible paper--Thin, delicate, made of vegetable fiber; used for engravings.
Safety paper
Duplex paper

Selecting paper