Patent ID: 6436176
Filing Date: 2002-08-20
Classification: B41N

Abstract:
A concentrated dampening solution for use in a lithographic printing process having a pH between 3 and 6 and comprising a water-soluble organic solvent, a phosphate salt in an amount, expressed as NaH2PO4 between 4 and 30 g/l and a transparent pigment, characterized in that said transparent pigment is a modified silica in which the silica particles have a number average size of 0.003 to 0.100 &mgr;m and in which the silica particles are coated with chemically combined atoms of an amphoteric metal which forms an insoluble silicate at a pH between 5 and 12, said metal atoms being chemically bound through oxygen atoms to silicon atoms in the surface of said particles, and the amount of said metal being such that: Gram atoms M/Gram atoms Si=A/1250 to A/250000 where M is the metal and A is the surface area of the particles of the silica sol expressed in m2/g.