Unit 1 - Paper and boards

What are 5 sources of cellulose?

flax, hemp, straw, cotton, bamboo

What is acetic acid used for?

To break down lignin that bonds cellulose fibres.

How is wood free pulp made?

The solution is heated to 140 degrees Celsius which produces a fibrous liquid known as pulp.

How much water does it take to make one A4 sheet of 80gdm photo copy paper?

500ml of water ---> nearly all of this is filtered and reused

Give the six main characteristics that papers and boards are categorised by.

Whiteness, opacity, strength, absorbency, finish and cost.

How would you reduce a paper’s absorbency?

By sizing it. Sizing agents are chemicals added to the pulp and rolled into the base layer.

What’s surfacing sizing for?

Added to improve strength and absorbency, which improves printability.

What’s the purpose of a coated finish?

Coated finishes reduce ink absorption which results in brighter, richer and sharper images with a deeper black.

What are the two main coatings and what are their properties?

Clay increases the smoothness of the paper/board and Polyethylene increases the gloss and wet strength.

What’s an advantage of uncoated paper?

The absence of sealant allows for greater and faster absorption.

What is the purpose of Die cutting?

It allows for the paper and board to be cut in one action, so it is often used for large quantities of identical shapes (e.g. nets for packaging and stationary products).

What’s the anatomy of a Die cutter?

Metal blades (usually steel) are embedded into the desired shape. Rubber is placed around each blade, so when pressure is applied the blade is revealed and cuts the paper.

Describe creasing.

Making a line that is permanently present.

Describe scoring.

same process as cutting but the blade doesn’t go all the way through the material, the score lines partially cut the material allowing a sharp edge or joint to be create that can articulate accurately.

What are perforations?

Small cuts in the paper or board allow for portions to be folded or torn off with accuracy. They are usually created with a perforation rule in a die cutter.