Paper is a mat of plant fibres. The raw material is thus paper pulp, produced from a variety of fibres:
Fight like rag "Who has not heard that phrase recalling many quarrels between the recovery of precious cloth! Legs, flags, Peille, drills ... tasty names to designate the raw material for paper Manufacturers of yesteryear. But beware, it uses only the beautiful cloth, clean, well sorted into categories according to its characteristics (brightness, color, ...)
From the book Art and Paper, Marie-Hélène Reynaud, Textual Editions
Paper pulp, in the form of sheets, is mixed with water. Then, ingredients are added to the pulp to give the paper the desired qualities for its future use:
How to recognize a piece of paper that is dyed at the pulp level or at a later stage of the manufacturing (on the surface)? Just tear the paper. The dyed paper is colored on the inside as well as on the surface . Otherwise the paper is a different than its core.