COMPOSITIONS OF CALCIUM CARBONATES/PIGMENTS FOR PAPER FORMULATIONS, SHOWING PRINT THROUGH REDUCTION

The present invention relates to mixtures of two distinct porous, stable aggregates and rather coarse PCCs (precipitated) calcium carbonate pigments (such as a composition comprising a blend or mix of one of the two Grade B or Grade C PCCs, in combination with a second, specific S-PCC (S=scalenohedral type PCC) pigment in a ratio appropriately selected between 90/10 and 10/90 percent by dry weight, namely 80/20 and 20/80, with a coarser, third component, which may be a pigment and/or a filler such as natural calcium (ground) carbonate or (most preferably) a PCC (precipitated calcium carbonate), depending on the granulometry of the two fine PCCs the third, coarser component, may be omitted. The main criteria for selecting the said "coarser" pigment is that it should feature a granulometry which does no affect noticeably, when in admixture with the blend PCC Grade B (or PCC Grade C) with S-PCC the finest part of the granulometry data of the blend, and in particular that it should not contribute anything significant to the amount of particles