paper
Paper has a long history, beginning with the ancient Egyptians and continuing to the present day. For thousands of years, hand-made methods dominated and then, during the 19th century, paper production became industrialised. Originally intended purely for writing and printing purposes, a wide variety of paper grades and uses are now available to the consumer
Of all the writing and drawing materials that people have employed down the ages, paper is the most widely used around the world. Its name derives from papyrus the material used by the ancient Egyptians, Greeks and Romans. Papyrus, however, is only one of the predecessors of paper that together are known by the generic term tapa’ and are mostly made from the inner bark of paper mulberry, fig and daphne.
Tapa has been found extensively in nearly all cultures along the Equatorial belt and is made by what is possibly the oldest papermaking technique – one still practised in some parts of the Himalayas and South East Asia. Indeed, recent archaeological excavations in China have revealed some of the oldest tapa’ paper ever found which shows that paper was being produced in China before western records began.
The tapa technique involves cooked bast, which is flattened with a wooden hammer to form a thin, fibrous layer and then dissolved in a vat with water to make a pulp. A screen consisting of a wooden frame with a fabric base is then laid in a puddle or big basin and floats with the fabric just under the surface of the water. The papermaker then pours the quantity of pulp needed to make one sheet into this floating mould’ and spreads it evenly, by hand, across the surface. The screen is then carefully lifted out of the water, allowed to drain off and a sheet of paper forms on the wire. Once the water has dripped off, the screen is placed in the sun or near a fire to dry. When dry, the sheet easily peels off and, apart from possible smoothing, requires no further treatment. This technique has two basic drawbacks. Firstly, a separate screen is needed for each new sheet, and is only available for use again after the last sheet has dried. And secondly, an increase in production can soon lead to a shortage of raw material, since fresh bast is not always available everywhere in the required quantity.
The fibres normally used for textiles, like flax and hemp, also served as substitutes for bast. In later times, the fabric was replaced by fine bamboo sticks, which freed the papermaker of the need to let the paper dry naturally in the mould, since the poured or ladled sheet could be couched’ off.
The history of the paper industry in the 19th and 20th centuries can be broken down into five partly overlapping periods, each marked by definite trends.
In the first stage (from about 1800 to 1860), all work sequences previously performed by hand were mechanised. This included the rag preparation, the use of fillers, pulp beating, the paper machine with its various parts, and the machines required for finishing the paper (the headbox, wire section, press section, dryer section, units for reeling, smoothing and packaging).
During the second stage (about 1840 to 1880), efforts were made to obtain rag substitutes on an industrial scale (groundwood pulp and chemical pulp) and appropriate industrial plants (groundwood and chemical pulp mills) were developed.
The third stage (1860 to 1950) was marked by the enlargement of the web width, an increase in working speeds, the introduction of electric drive and further improvements to various machine parts. Machines designed specifically for the production of particular paper and board grades (for example the Yankee cylinder and multi-cylinder machines) were also developed. The web working width grew from 85 cm (1830) to 770 cm (1930), while production speeds rose from 5 m/min. (1820) to over 500 m/min. (1930).
The fourth stage (1950 to 1980), which was still dependent on the old methods as far as the mechanics were concerned, brought unprecedented changes in papermaking. Alongside further increases in web width and working speeds, there was the use of new materials (thermo-mechanical pulp, deinked recovered paper, new fillers, processed chemicals and dyes), new sheet forming options (e.g. by twin-wire formers), neutral sizing, greater stress on ecology (closed loops) and, most of all, automation. The operational impact of these changes was: specialisation in certain paper types; development of new paper grades (LWC – lightweight coated paper); corporate mergers; company groups with their own raw material supply and trading organisations; closure of unprofitable operations.
1980 onwards
The fifth stage leads into the future. The evolution of new sheet-forming principles (with fluid boundaries between paper and non-woven fabrics) and chemical pulp processes have been the main process improvements. However, the situation on the global market (increased demand, above all in the Third World, trends in chemical pulp prices, problems of location), are again raising capital intensity and encouraging the formation of big company groups with international operations. At the same time there are definite opportunities for smaller, local firms satisfying specific needs.