Question

What is pulping? How is uncoated paper converted into coated paper?

Answer 1

Paper is obtained from the wood. But wood is very hard. In order to make paper from the wood we have to extract the fibres from the wood.

Complete Answer:
Pulping: Pulping is the process of extracting fibrous material such as cellulose from the wood. Pulping is the important process in papermaking as it makes pulp which is used as a raw material for the paper production from the wood. Pulping is an essential step because wood contains other substances also from which the pulp has to be extracted. Pulp contains Cellulose, lignin and hemicellulose. Pulping from the wood can be done mechanically, thermally or by using some chemical treatment such as sulphur extraction.
Process of converting uncoated paper into coated paper.
Uncoated paper is made coated in which paper is coated with certain polymeric substances to impart a specific property to the paper. Such as changing the weight of the paper, making the paper surface smooth and glossy, reducing its ink absorption of the paper. Coating also used to make high quality paper used for the packaging purpose.
During the coating Paper can be treated with the clay coating (Kaolin). This can be done by adding uncoated paper in the prepared slurry of the clay. We also have to use binder for the better attachment of clay to the paper. Such paper then passed into the roller in which it is rolled to make the surface of the paper smooth and glossy.

Additional Information:
There are two major types of coated papers 1) Machine Finished coated paper: they are glossy and strong paper and are mainly used for making paperbacks. 2) Coated fine paper: They are mainly used for offset printing, as an art paper etc.

Note: During the coating clay slurry must also be passed through the filter to remove any kinds of impurities, otherwise even a firm coating can’t be done.