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Part 15 - Paper

The use of chlorine for bleaching was discovered in 1744 and by the end of the 18th century the raw material for paper was bleached cotton and, in 1806, animal gelatine and starch sizes were replaced with aluminum sulphate and resin.

Although cheaper than vellum, paper remained relatively expensive until the invention, in the19th century, of steam-driven paper making machinery that used wood pulp fibres. Nicholas Louis Robert was granted a French patent for a continuous paper making machine in 1799. In London, Henry Fourdrinier, agreed to finance the project and a British patent was granted in October 1801. An improved version of Robert's original design was installed at Frogmore Paper Mill, Hertfordshire, in 1803. It produced paper continuously with a forming section (wet end), a press section and a dryer section.

The increased demand for paper and an inadequate supply of cotton rags drove the need to find alternatives. However, experiments with wood fibre were not successful until in 1844 when Friedrich Gottlob used a grinding wheel to free the fibres from wood. Also in 1844, Canadians Charles Fenerty and F.G. Keller improved the machines to use wood pulp for papermaking. These developments started a new era for the production of newsprint and by the end of the 19th-century almost all paper was made out of pulped wood. Most of the raw material being waste wood from the manufacture of timber construction materials.

The modern paper mill produces a continuous roll of paper rather than individual sheets. Some mills produce paper 10 metres (400 inches) wide at a speed of 100 km/h. (60 mph). Sheets of paper are then made by slitting the paper to width (typically 8.5 inches) with rotary disk scissors and then sheared in to length (typically 11 inches to form a standard page sized sheet).

The process starts with a pulp in which the raw pulp is refined and mixed in water with additives. The head-box of the paper machine distributes the slurry onto a moving, continuous sieve-like screen. Water drains from the slurry (by gravity or under vacuum), so that the pulp becomes a mat of randomly interwoven fibres. More water is removed by pressing rollers, aided by suction or heating. Once dry, the strong, flat, uniform sheet of paper is wound onto drums for printing or further processing. These large rolls of paper often weigh many tons.

The invention of the steam driven rotary printing press, the fountain pen, the mass-produced pencil and an increase in literacy at that time transformed 19th century economies. With the introduction of cheaper paper for letters, diaries, schoolbooks and fiction and non-fiction books as well as newspapers, the demand for paper gradually increased.

There were problems with paper made from stone groundwood pulp. It tended to yellow with age because of the lignin in the wood. Also the original paper was prone to disintegrate through a process known as slow fire, caused by the use of alum. So quality paper continued to be produced from more expensive but stable rag paper. However , modern, mass-market paperback books continue to use the cheaper mechanical papers.  Modern books now are made with acid-free paper for hardback and trade paperback books.

At the end of the 19th century a bleaching process was developed in Scandinavia, which removed lignin from stone groundwood. This greatly decreased the yellowing of paper with age so that cotton fibre from rags was no longer needed as a raw material. In 1985 bleaching with chlorine was replaced with bleaching with chlorates and chlorine dioxide.

In the twentieth century, some plastic "paper" was introduced, as well as paper-plastic laminates, paper-metal laminates, and papers infused or coated with different products that give them special properties.

Corrugated (also called pleated) paper was patented in England in 1856, and used as a stiffening liner for tall hats. Corrugated boxboard was patented in 1871 by Albert Jones of New York City for single-sided (single-face) corrugated board used for wrapping bottles and glass lantern chimneys. The first machine to produce large quantities of corrugated board was built in 1874 by G. Smyth, and in the same year Oliver Long improved upon Jones' design by inventing corrugated board with liner sheets on both sides, thereby inventing corrugated board.

The Kellogg brothers were among first to use paperboard cartons to hold their cornflake cereal. The Kieckhefer Container Company was another American packaging industry pioneer producing fibre shipping containers and particularly paper milk cartons.

Robert Gair invented the pre-cut paperboard box in 1890 when he accidentally discovered that by cutting and creasing in one operation he could make prefabricated paperboard boxes. Applying this idea to corrugated boxboard was a simple development. The corrugated box was first used for packaging glass and pottery containers and by the mid-1950s, they were used to ship fruit and vegetables without bruising, improving the return to producers and opening export markets. The use of paperboard quickly spread to almost every type of product.

Corrugated fiberboard, is made by sandwiching a fluted or corrugated sheet of containerboard between two flat linerboards. The corrugated sheet and the linerboards are made of kraft containerboard, a material usually over 0.01 inches (0.25 mm) thick. Double or triple (tri-wall) corrugated fiberboard is also made for larger or more easily damaged products.