With the actual ratios between long fibre and middle fraction a larger contribution to light
scattering in a fines free pulp will be given for groundwood pulp than for TMP. That is why a
higher light scattering coefficient is always reached for groundwood pulp at a given fines content.
A prerequisite to get a high light scattering from a TMP process is to have access to a thin
walled type of wood, which gets a long fibre fraction with a high light scattering ability