The aim of the pulping process is to break down the structure of the fibre source into the fibres ready to be made into market pulp.
To achieve this the fibres are put through either of the two processes that are used to develop the pulp. The two process are mechanical pulping or chemical pulping (otherwise known as kraft).
The chemical process, as you may have previously read involves cooking the wood shavings in a sulphate solution to digest the wood. Both sulphate and sulphite can be used to separate the fibres from the lignin which, is a natural glue like substance that bonds the fibres.
Chemical pulping degrades the lignin into small water soluble molecules which can be washed away without weakening the fibres. The result of the chemical process is either a dark brown in colour or, it can be bleached during the procedure resulting in a white kraft.
Mechanical pulping however involves grinding debarked logs against a revolving stone or disk grinders in order to break down the fibres to make a pulp.
The stone gets sprayed with water to remove the fibres, this however results in very little removal of lignin meaning paper quality is reduced, which therefore also indicates that the strength of the fibres may have been impaired from the process.
Mechanical pulping however is a low cost solution which generates a higher output.
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