Rugby School Thailand Design & Technology Senior School

L9. Paper Classification / Stock

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By the end of this unit you should have developed a knowledge and understanding of:

where paper comes from and how pulp is converted into workable materials
the common stock sizes and forms of paper and card,
the properties of paper and board,
the differences between paper, card and board
how boards can be laminated to other materials enhance their properties.
common uses for different types of paper and board

Glossary:

Compliant - Easy to manipulate / work with

GSM - Grams per square meter

ISO - International standards

Laminated - Layered

Paper based (compliant) products can be put into three categories.

*Note that there are various definitions of what constitutes paper, card or board:

Paper

Thin, with a weight up to 200GSM

Cartridge, tracing, layout, Watercolour

Card

Heavier with a weight over 200GSM

Duplex card, Box card

Board

Thicker than card and up to 500+ GSM

Mounting board, foam board

Sources and origins

Paper, card and board are made from wood pulp which is extracted from the fibres found in wood. See the section on wood and timber for more information.

Wood is made up of cellulose fibres which are glued together with a natural product called lignin. In order to make paper pulp, the lignin needs to be removed so that the cellulose fibres can bind together to form paper.

The wood is crushed and the extracted material is 95% water based pulp which looks a bit like milk.

It is then passed through dryers and rollers to achieve the basic quality of paper.

Wood pulp

Lignin and Cellulose

Stock forms of paper

Paper and board comes in sizes that correspond to each other called the International Standards Organization (ISO) system.

Common stock paper sizes

The A size is the standard for most general printing and stationary. Each size can be halved while increasing the A number. For example:
A0 is the largest standard stock size; often used for architectural drawings.
A1 is often used for artwork and posters
A2 is used for smaller artwork
A3 is a standard size used for D&T portfolios.
A4 is usually used for business stationery, brochures, booklets etc.
A5 is commonly used for smaller items such as leaflets/flyers etc.
A6 is the international postcard size.
A7 for labels etc.
A8 for business cards

The thickness of paper and thin card is measured in microns: a micron is 1/1000th of a millimeter. However, board such as corrugated cardboard can be quite a few millimeters thick.

Paper and Card Properties

Optical properties of paper products

As all paper products are derived from the same material, what makes them different are their optical and surface properties as well as their weight.

Cellulose is ‘jelly-like’ with translucent qualities which, when compressed lightly, makes paper that can allow light to pass through it.

Layout paper and tracing paper are examples of this.

To make paper more opaque, the pulp is compressed further making it less translucent, and adding thickness makes it more opaque. Paper can be coloured or have additional layers of materials added to it.

Optical Properties also include brightness, colour, opacity and gloss.

Opacity refers to how much you can ‘see through’ the paper.

Gloss, glare, finish and smoothness refer to how glossy or reflective the paper is while finish refers to the general surface characteristics of the paper e.g. rough

Strength and durability refer to how strong the paper is. Paper strength is dependent on thickness and greatly affected by moisture.

Tensile strength refers to how strong the paper is when stretched while bending strength is how flexible the paper or board is.

Porosity is how much the paper will absorb moisture. For example, greaseproof paper has little porosity.

Changing the finish

We need a variety of different finishes on paper but how do we get them from the same paper material?

Coating

In order to get a smooth finish on paper or card it is sprayed with china clay or chalk.

sizing

The addition of a sizing agent improves the ability of the paper or card to accept ink by sealing the absorbency of the surface. Both coating and sizing directly affect brightness.

Laminating

Paper and card can also be laminated. Layers of thin card are stuck together. Depending on now many layers are stuck together you can change the qualities of the card.

Key concepts

Cost

Basically people choose paper based on cost which is why newsprint for newspapers is so cheap, but photo paper is expensive.

finish

This is how the material looks and feels and varies depending on what you are using it for.

strength

How strong the paper is. Newsprint is cheap and doesn’t need to last long but packaging for expensive perfume needs to be much stronger.

brightness

AKA Whiteness

Basically how white the paper is and, as it reflects light, it will appear brighter.

thickness

How thick the paper is, as it gets thicker it becomes card then board.

Summary

Weight or thickness define the material as paper or board.
Card is another name for board which is thick paper.
The difference between paper and card or board is the thickness or weight.
Paper is sold by weight in grams per square metre (gsm) up to approximately 200 gsm at which point it becomes card/board.
Board is often defined by its thickness or layers which can be measured in microns or millimeters for thicker boards.
There are 1000 microns in 1mm and a typical birthday card is 300 microns thick compared to the thin paper in your text book which is 90 microns thick.
Here is the list of common paper products in order of their GSM.

Paper - up to 200 GSM

Newsprint (35-50GSM)

is very thin and used for newspapers.

Layout Paper (50GSM)

is used for sketching and development work.

It is thin enough to trace over existing drawings.

Layout paper is used by designers particularly in advertising where it can be used to traced over previous sketches building up concept ideas with each layer.

Tracing Paper (60-90GSM)

Is translucent and its hard surface allows ink to be scraped off. Tracing paper and drafting film are more translucent than layout paper and used for tracing and for technical drawings respectively.

Cartridge Paper (120-150GSM)

is higher quality drawing paper, cream and slightly textured.

Cartridge paper is thicker than printer paper but not as thick as watercolour paper and often has a textured surface to encourage the transfer of pencil, chalk and pastels. It is the paper of choice for artists but can also be used for high quality letter printing/writing.

Photocopier Paper (80GSM)

is cheap when bought in bulk.

Printer paper is used extensively in printers and laser copiers etc. It has a

smooth surface and is also ideal for general writing and drawing.

Sugar Paper (100GSM)

is available in a range of colours and is often used as the backing for wall displays in school. The colours are easily bleached out.

Bleedproof paper (120-150GSM)

is used for marker work as it has a barrier which stops ink from ‘bleeding through’ the paper.

Bleedproof paper has a protective layer on the underside to stop ink bleeding into the next sheet. Often used for marker work.

Watercolour paper

Watercolour paper is a thick paper which, unlike cartridge paper, has better resistance to wrinkling and creasing when wet.

There are three main textures available in watercolour papers.

Hot pressed paper with a hard, smooth surface.
Cold pressed papers with a rougher surface but better absorption
A third type, which is rougher than cold pressed

Recycled paper

Where does recycled paper come from?

We saw that paper products are made from pulp which originally derived from wood, but it can also be recycled from waste-paper products.

The pulp is a grey brown colour and needs to be bleached to make white paper which adds to the expense, but it needs to be white if it is to be printed on so the colours are not compromised.

Turning wood into paper

Prep 9

Card, Board & Uses >

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