PAPER What is it?

Paper is a thin material mainly used for writing upon, printing upon or for packaging. It is produced by pressing together moist 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;

• 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.

Some properties of paper are:

physical properties: o specific weight (paper: < 140g/m2; light cardboard: 140-400 g/m2; cardboard: >400

g/m2); o flexibility: you can turn the pages of your books many times without damaging them; o folding: paper can be easily folded and maintains the folding

Mechanical properties: o Traction resistance o Tear resistance o Bending resistance

Printability: (paper receives ink without developing rings or halos) and eraseability Appearence: colour, transparency, smoothness, etc.

Paper formats: 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).

What is its use?

Paper is a versatile material with many uses. Its most common use is for writing and printing upon, but it is also widely used as a packaging material, in many cleaning products, in a number of industrial and construction processes. Here is a list of its main uses:

For representing value: paper money, bank note, cheque, tickets For storing information: book, notebook, magazine, newspaper, art, letter For personal use: diary, notes, scratch paper For communication: between individuals and/or groups of people. For packaging: corrugated box, paper bag, envelope, packing & wrapping paper, wallpaper For cleaning: toilet paper, handkerchiefs, paper towels, facial tissue and cat litter

For construction: papier-mâché, origami, paper planes… For other uses: sandpaper, blotting paper, litmus paper, filter paper and other chemical

laboratory uses.

When was it invented?

Paper was invented in China about 2200 years ago. Even though it's been around for that long, it was a long time before people around the world started making paper.

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 woodentablets covered with wax, or parchment, or papyrus sheet. In Europe, sheep skin (parchment) was used for important documents and handmade books

for centuries

Paper making technology spread from China through the Middle East to medieval Europe in the 13th century, at the end of the Middle Age.

How is it made?

Paper is one of the most common uses of wood, although it can be obtained also from some weeds or by recycling cotton rags. The most used wood comes from hardwood trees (poplar, birch, beech) and softwood trees (pine, larch).

After cutting the trees, bark must be removed from logs. Then the wood is finely chopped and mixed wih water; acid is added to remove lignin. After that treatment, almost only cellulose and water is left. Cellulose fibers are more finely chopped, 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.

With superficial treatments you can also produce several paper textures: smooth, rough, glossy paper.

Is it recyclable?

Yes! Paper can be recycled. In Italy almost half of the paper used comes from the recycling process.

The recycling process has 2 phases: the pulping of wastepaper and then the cleaning process, where all impurities, such as ink and glue, are removed. The following steps are similar to those in the making of paper from wood.

For a very good presentation of the modern paper making process, you may watch this video: http://www.youtube.com/watch?v=E4C3X26dxbM