Common fillers are precipitated and ground calcium carbonate, kaolin clay, talc and titanium dioxide. Their small particles create many air interfaces, so they scatter light far better than fiber, raising opacity and brightness while replacing more expensive pulp. Filler weakens the sheet by getting between fibers and reducing bonding, so levels are set against strength and dusting limits.
Filler is up to 24 percent ash and the sheet is starting to dust on press, so we're at the limit.
Filler that is not retained ends up in the white water and the effluent, so first-pass ash retention is watched as closely as the dose.
Also heard as
- loading
- loading material
Related terms
PCC
Precipitated calcium carbonate: a synthetic filler, often made beside the mill, that raises brightness and opacity.
TiO2
Titanium dioxide: the most powerful white pigment for adding opacity, used where every point of opacity counts.
Ash content
Mineral residue left after burning a paper sample, used to estimate filler and coating pigment content.
Opacity
A sheet's ability to hide what lies behind it, expressed as a percentage from readings over black and white backings.
Light-scattering coefficient
Per-grammage measure of how strongly a paper redirects light, written s and given in square meters per kilogram.