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Lecture notes on Technical principles - UNIT 1
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Extensive and easy to understand classnotes for Unit 1 - within technical principles for paper 1. These helped me achieve an A* throughout the course.
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1️⃣ Performance characteristics of paper & boardsWhat is paper + board made from?
Made from cellulose fibres derived from plants
Most common source: waste sugarcane
1. Sweet juice is extracted from the sugar
2. Shredded cane (bagasse) is processed to make popular paper products
The best cellulose fibres for paper production comes from wood (deciduous + coniferous trees)
Due to quality of the fibres length + strength
Sources of cellulose
Bamboo
Cotton
Flax
What are paper properties?
Whiteness - including level of brightness
Opacity
Strength - does it resist tearing?
Absorbency - for water or ink?
Finish - matt satin or gloss
Cost - to match a price point
What goes into making paper?
Acetic acid is used to break down the lignin that bonds the cellulose fibres
Fillers (e.g. clay/calcium carbonate) are often added
Reduce costs but affect the performance
Brightening agents (e.g. bleach)
Lots of water
Wood free pulp
The solution is heated to 140*C, which produces a fibrous liquid, known as pulp
It takes a minimum of 500ml of water to make one A4 sheet of paper (80gsm photocopy paper)
Dyes + sizes can be added to the pulp depending on the desired final appearance
, Almost all the water is filtered + reused
After the cooking process the remaining, lignin free, fibres are called 'wood free' pulp
Creating the perfect paper (5 ingredients that can be adjusted)
1. Source of cellulose fibres
2. Fillers - that smooth out the finish of the paper
3. Sizing agents - that increase absorbency
4. The calendaring process - using different rollers to create specific thicknesses + surface finishes
5. Additional finishes (e.g. UV varnish / texturing)
Sizing agents
Sizing agents: chemicals added to pulp or sprayed + rolled to the base paper
Internal sizing
affects paper quality and the paper's ability to run smoothly through machines
Surface sizing
added to improve strength, reduce absorbency + hence improves printability
Coated and uncoated finishes
The application of surface sizing is the main difference between coated and uncoated stock
Coated paper reduces ink absorption => brighter, richer + sharper images with deeper blacks
Two main coatings
Clay - increases smoothness
Polyethylene (PE) - increases gloss + wet strength
Uncoated paper is not treated with any sealant, which increases water/ink absorbency
The printing ink goes deeper into the paper rather than just drying on the surface
Colours appear dull + the paper is weaker compared to coated paper
Pros are that it can be given a wide range of textured finishes (e.g. napkins)
(General) paper + board finishes
Matte - smooth + dull in appearance - good for any high quality print job
Satin - has lower reflective levels than gloss paper, but more than matte
Gloss - is a shiny, higher quality coated paper
Textures - created with a felt roller covered in woven wire
Felt, wove + velum are increasingly smooth textures
Column, linen + laid have lines at different depths and positions
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