The formula for calculating the tightness of paper is:
D = G/σ
In the formula
D——paper tightness, g/cm³;
G——weight of paper, g/cm²;
σ——thickness of paper, cm.
The tightness of paper is also a basic performance index of paper, which affects the mechanical and optical properties of paper to varying degrees. Generally, the higher the tightness of the paper, the better its mechanical properties such as burst resistance and tensile strength, but the poor air permeability is not easy to print through. The tightness of the paper has a great influence on the ink-absorbing performance of the paper. The ink-absorbing performance of the paper with high tightness is poor. For example, letterpress paper and newsprint require fast ink-absorbing, so the tightness should not be too large. National standards and ministerial standards stipulate tightness requirements for various printing papers, as shown in the table below.
