Dating pepr

In the TMP process, wood is chipped and then fed into steam heated refiners, where the chips are squeezed and converted to fibres between two steel discs.In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones to be made into fibres.Soda pulping is another specialty process used to pulp straws, bagasse and hardwoods with high silicate content.There are two major mechanical pulps: thermomechanical pulp (TMP) and groundwood pulp (GW).Most recycled paper contains a proportion of virgin fibre for the sake of quality; generally speaking, de-inked pulp is of the same quality or lower than the collected paper it was made from.There are three main classifications of recycled fibre:.Drying involves using air or heat to remove water from the paper sheets.In the earliest days of paper making, this was done by hanging the sheets like laundry; in more modern times, various forms of heated drying mechanisms are used.

Paper recycling processes can use either chemically or mechanically produced pulp; by mixing it with water and applying mechanical action the hydrogen bonds in the paper can be broken and fibres separated again.

The paper may then undergo sizing to alter its physical properties for use in various applications. Coated paper has a thin layer of material such as calcium carbonate or china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens.

(Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by calendering.

Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets.

It is a versatile material with many uses, including writing, printing, packaging, cleaning, decorating, and a number of industrial and construction processes.

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