How does used paper get recycled into clean 'new' paper?  First that old paper has to be deinked, broken down into fibers and bleached.  After that, the pulp can get reformed into 'new' paper.   This 222 page book, published as part of the Technical Association of the Pulp and Paper Industry (TAPPI), documents the state of the art in 1967. Has it changed much since then?  Got me, but probably not a lot.