Both lignin and extractives precipitate on the
pulp surface at pH values below 6. Most of the precipitated
lignin was found on the pulp surface after
sheet forming, whereas the main part of the precipitated
extractives could easily be washed away
with water. The combined ESCA, ToF-SIMS and
AFM results suggest that the precipitated lignin
formed a thick granular phase on the pulp surface,
while the precipitated extractives formed a very
thin film that may cover a large part of the pulp
surface, including the lignin. The film is probably
considerably thinner than the thickness of surface
layers probed by ESCA.