Sorry, one of my formaulas is incorrect: > 1 sheet (56x76 cm) of 300 g/m2 paper has a CaCO3 content of > 0.56*0.76*2/100 = 2.55 g becomes 0.56*0.76*300*2/100 = 2.55 g Alberto www.facebook.com/alberto.novo.1 www.grupponamias.com www.alternativephotography.com/wp/photographers/rodolfo-namias-group