Papermaking on a fourdrinier papermachine
PAPERMAKING ON A FOURDRINIER PAPERMACHINE
Paper is most often made on a fourdrinier papermachine. The major stages of papermaking on a fourdrinier are the following:
1. The fibres are mixed with water in a pulper.
2. The fibre mixture is refined, i.e. the fibres undergo a treatment aimed at improving their mechanical characteristics and matting.
3. The mixture, or pulp, is poured onto a continuous moving mesh known as the "forming table". The fibres intertwine on the mesh and form a sheet, once the water has been drained off.
4. The water is progressively removed through gravity, then by suction devices under the mesh. This is the stage when certain sheets are marked, using a roller with a relief pattern which will leave its imprint in the sheet – either in the form of laid lines (laid paper), or designs.
5. The sheet has then lost enough water to be laid on wool felt or synthetic felt, which will give the paper its grain. The paper then goes through presses consisting of steam-heated cylinders (the dryer section) where it will lose more water.
6. In order to improve the surface of the paper, a layer of gelatine is laid on top of the paper by a machine called a "size-press". This coating gives the paper its final surface qualities.
7. The paper goes through another dryer section in order to eliminate more water through contact with steam-heated cylinders.
8. As a last stage, the paper is wound onto a reel called the "mother reel". Depending on the qualities of the paper, its grammage, and the characteristics of the paper machine, the weight of the reel may range from a few hundred kilos to tens of tons!
To be read
- Traditional papermaking: cylinder mould