Effect of Formation on Print Unevenness, 1991 International Paper Physics Conference Proceedings
The relationship between paper formation and print unevenness has been studied with uncoated woodfree papers. Formation has been measured using beta-radiation and both commercial papers and paper made on an experimental paper machine were investigated.
Two different approaches have been used. First, absolute print unevenness has been compared to level of formation. The results indicate a clear connection between these two, although with commercial papers the correlation was not very strong. The reason is that in commercial paper making there are a lot of variables other than formation that affect print unevenness. On the experimental paper machine a strong correlation was observed.
The second approach was to compare local grammage values to local print density values ("pointwise correlation"). A typical value for the correlation was relatively low, r = 0.5. This correlation also varies strongly as a function of calendering.
Effect of Formation on Print Unevenness, 1991 International Paper Physics Conference Proceedings