Hard water
Water's hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are positively charged metal complexes with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca and Mg. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they contain few ions.
Paper and ink testing
% of moisure content in the paper is known as relative moisure content.High moisure content will increase the weight of the paper and increase the cost of paper. At the same time low moisure content will make the paper brittle and increases the chances of break in production.Roughness indicates varying degree of porosity of the paper. Porosity is a direct indication of paper to accept ink or water.