These papers are intended for use in the book. Available in a variety of different weights, surfaces, tones and colors. Sew these papers into sections to create your own book block. Our book papers have a smoother surface making them ideal for book pages and drawing. GSM: (metric measurement) grams per square meter. The gram weight of a hypothetical square meter of a particular type of paper, a good comparative measure because it does not vary with sheet size. LB: (imperial measurement) Paper weights are measured depending on the most popular end use of a particular grade (examples: “text paper”, “cover paper”, “bond paper”, or “writing paper”). Each of these paper weight categories has its own “basis size” from which to calculate its weight. This weight is determined by weighing 500 sheets of each basis size. For example, the basis size of “text paper” is 25″x38″ and “cover paper” has a basis size of 20″x26″. When referring to the weight of an imperial measured paper be certain to reference the particular identity of the paper, because 80lb text & 80lb cover have very different thicknesses. But, as a general rule of thumb the higher the paper weight, the thicker the sheet of paper.Rough or cold press papers can also be used as book papers, and can found on our Watercolor and Printmaking paper pages.