Precipitated or synthetic calcium carbonate, also in crystalline form, but of greater purity than natural (the properties cited are similar, except for the pH value that ranges between 9 and 10 and the size, which is much finer, approximately 0.06 µm). Precisely, the dissimilar particle sizes lead to very different oil absorption rates, greater than that of the synthetic extender (approximately 26 ml / 100 g). The low absorption of the latter allows the use in anticorrosive paints to achieve a high critical PVC and decrease costs, in outdoor products it increases resistance to chalking.
