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The British Wood Pulp Association

Thermo-Mechanical-Pulp (TMP) and Chemi-Thermo-Mechanical-Pulp (CTMP) are a combination of the mechanical and chemical processes.

De-barked logs are chipped in both, then reheated to extreme temperatures to soften them before passing through grindstones for mechanical reduction to fibres. The difference is that chemicals are sprayed onto the chips in the CTMP process to reduce the undesirable effects of the retained natural wood substances.

The main disadvantage of this form of pulping is the high energy demand. Both processes give high pulp yields, but papers made from them have inferior ageing qualities compared with those made from chemical pulps.