Paper, Card & Boards

• paper, card & board consist of processed wood fibres

• cotton, straw & hemp can be used to create product with modified properties

• SOFTWOOD - longer fibres - stronger product

• HARDWOOD - shorter fibres - smoother & more opaque product

• PULPING PROCESS - separates wood fibres (which are bound wih lignin)

• additives - improve properties of most wood pulps

1) Mechanical Pulp - lower quality

• timber is soaked, debarked, ground & screened.
• inexpensive, high yield
• additives (eg peroxide, sodium hydroxide) can be used to improve properties

2) Chemical Pulp - higher quality (due to less impurities & formation of longer fibres)

• timber is debarked, cut to chips, pound & screened then treated with chemicals to remove unwanted constituents.
• expensive, lower yield

3) Waste Pulp- low quality because recycling results in shorter fibres

• recycled paper & card are pulped, impurities (eg ink) are removed chemically &/or mechanically
• to improve virgin fibres can be added, bonding agents, sizing agents & pigments
  

Paper is produced on fourdriner machines. It's a continuous process.

1) A continuous stream of diluted pulp is fed onto a vibrating mesh belt - which allows water to drain & encourages fibres to interwaeve

2) More water is removed by squeezing the pulp under another mesh

3) A dandy roll smoothes the fibres

4) Roller & heated cylinders dry the paper, additives & coatings are introduced by spray or press

5) More water is removed using suction boxes & rollers allowing the paper to move unsupported through the process

6) Highly polished rollers (called calenders) can be used to produce a smooth gloss, finish

Paper & board can be categorised by thier size, weight or thichness, colour, opacity, surface finish & texture, cost, ability to accept graphics media.....

• uncoated - eg copier paper (80gsm, lighweight, smooth, bright white or coloured, inexpensive)

• coated paper - eg coated inkjet paper (80-150 gsm, bright white, high density, smooth, expensive)

• specialist paper - eg embossed paper, wrapping paper & marbled paper (various types & weights, decorative surface or texture)

• card & board - eg mounting board, cartonboard & corrugated board (1000-1500 microns, ver thick, high quality, ver expensive, smooth or textured colour layer applied to one surface)

..to enhance the properties of paper

BLEACH - to reduce colour impurities

SIZING AGENTS - to improve paper quality by reducing absorbancy (eg starch)

BONDING AGENTS - help bind fibres together

PIGMENTS - to improve colour quality

COATINGS - to improve paper quality

LAMINATES - to improve paper quality, strenght &/or durability