As a result, the majority of Book paper today is made from chemical wood pulp. Rag fibers are still used in the highest grades for certain characteristics, although it has been demonstrated that by using the best chemical wood pulp such paper has much of the characteristics and permanency of rag paper. No matter what the material used, paper cannot be permanent in color and strength unless carefully made, and acids or other deleterious materials eliminated. 6. Type of illustration, or printing process, to be used.

It is vitally important that the paper be selected with this in mind. For the type of paper to use most effectively with various line screen halftones, see 416 and 417.

Machine Finish Book paper has a medium smooth finish suitable for ordinary printing where the cuts used are not too fine and the requirements, from a printing standpoint, not too exacting.

A better grade of similar paper is called English Finish, which, having a more level surface, gives a better printing result than Machine Finish.

Both of the above papers are finished on the paper machine, but Supercalendered paper is polished after being made, giving a higher shine to the surface for sharper reproduction of the details in the cuts when desired. However, the polishing of Uncoated paper has some effect on color, hence Supercalendered papers are not so bright in color as Machine Finish or English Finish and are also somewhat lower in bulk.

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Calender Stacks Which Give Paper a Smooth Finish, and Winding Rol