Paper

© Vittoria Patti 2014

Paper is a thin materialmainly used for writing upon, printing upon or for packaging.

It is produced by pressing togethermoist fibers, typically

cellulose pulp derived from wood, rags or grasses,

and drying them into flexible sheets.

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;• Writing paper: notebooks, drawing, photocopies;

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;• Writing paper: notebooks, drawing, photocopies;• Wrapping (packing) paper: resistant paper used to wrap food, cement, grease proof paper;

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;• Writing paper: notebooks, drawing, photocopies;• Wrapping (packing) paper: resistant paper used to wrap food, cement, grease proof paper;• Cardboard: used in cardboard boxes;

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;• Writing paper: notebooks, drawing, photocopies;• Wrapping (packing) paper: resistant paper used to wrap food, cement, grease proof paper;• Cardboard: used in cardboard boxes;• Domestic paper: soft paper used for kitchen paper, toilet paper, napkins;

There are several paper categories:• Printable paper: paper used for newspaper and telephone books, books, photographic paper;• Writing paper: notebooks, drawing, photocopies;• Wrapping (packing) paper: resistant paper used to wrap food, cement, grease proof paper;• Cardboard: used in cardboard boxes;• Domestic paper: soft paper used for kitchen paper, toilet paper, napkins;• Others: wall paper, filter paper, glass-paper.

specific weight

Paper< 140g/m2

Light cardboard140-400 g/m2

Cardboard>400 g/m2

flexibilityit means that you can turn the pages of your books many times without damaging them.

foldingit means that paper can be easily folded and it maintains the folding.

Mechanical properties• traction resistance• tear resistance• bending resistance

Printability:

it means that paper can receive ink without developing rings or halos

and eraseability

• .

The sizing system in Europe is based

on common width to height ratios

for different paper sizes. The largest

standard size paper is A0 (A zero).

Two sheets of A1, placed upright

side by side, fit exactly into one

sheet of A0 laid on its side.

Similarly, two sheets of A2 fit into

one sheet of A1 and so forth.

Common sizes used in the office

and the home are A4 and A3

(A3 is the size of two A4 sheets).

In order to make paper, wood logs (or other fibrous material) have to be turned into something called pulp. This process is called pulping and it can be mechanical or chemical.

Wood is made of cellulose and lignin. The objective of pulping is to reduce wood to pure cellulose fibres. Lignin makes the paper quality worse and must be reduced.

.

Traditional mechanical pulping (also called groundwood) involves forcing logs against a revolving stone or blade, which grinds the logs into small pieces by friction.

This process does not remove the lignin, so mechanical pulping only creates paper of low quality, which tends to become yellow and weak.

(This is the paper used for newspapers, for example.)

In order to obtain a better quality paper, lignin can be removed in a following step, using some chemicals.

Cellulose fibers are more finely homogenised, added with some chemicals to provide some desired properties, and then spread on wide surfaces, letting water drain. The mixture is then pressed, dried and stored in big rolls, ready to be cut and delivered.

Paper was invented in China about 2200 years ago.

Before there was paper, people used different things for recording words: for example…

…the ancient Sumerians used clay tablets.

… Egyptians used papyrus sheets, obtained from a specific plant (Papyrus).

Actually, the term “paper” comes from “papyrus”.

…Greeks and Romans used

wooden tablets covered with wax,

or parchment,

or papyrussheet.

Paper making technology

spread from China through the Middle East

to Europe in the 13th century,

at the end of the Middle Age.

Paper can be recycled!

In Italy almost

half of the paper used comes from the

recycling process.

The recycling process has 2 steps:

1. the pulping of wastepaper,

2. the cleaning process, where all impurities, such as ink and glue, are removed.

The following steps are similar to thosein the making of paper from wood.