The percentage of light that passes through a sheet of paper. Some papers are more opaque than others because they contain more fibers and/or fillers. Papers containing more fibers and fillers have the ability to hold a printed image without the image showing through to the backside of the sheet. A paper that is thick does not necessarily guarantee that it is more opaque than a thinner paper. Some thinner papers may be more opaque because they contain a greater number of fibers and/or fillers in their composition.
