The sizing degree is one of the main characteristics of printing papers and appropriate sizing is needed to regulate the penetration of ink and water into paper.

A combination of aluminium salts and organic compounds (natural rosin size and synthetic size) have been used in the process since the 19th century.  

Aluminium sulphate was the first product used but in the 90’s it was replaced by poly aluminium chloride (PAC). Aluminium salts have always been essential components in different sizing formulations for papermaking.