When exam­in­ing paper, a print­er can look at four dimen­sions –

  • Gen­er­al qual­i­ty: this is the colour, look-through, fin­ish and strength
  • Price
  • Suit­abil­i­ty for pur­pose
  • Effi­cien­cy of con­di­tion: matu­ri­ty, free­dom from damp, flaws, bad edges and the con­di­tion of the coat­ing

Print­ing papers were pre­dom­i­nant­ly made from wood­pulp or espar­to.  Espar­to is a long, wiry grass from Spain and North Africa.  The fibres are short and soft and so not quite as strong as rag.  That said, espar­to stretch­es less and more even­ly than oth­er fibres.

In gen­er­al terms, ordi­nary machine paper that is strong and opaque is suit­able for book work pro­vid­ed that the fideli­ty of illus­tra­tion is not so impor­tant.  Imi­ta­tion art paper is based on espar­to pulp but has chi­na clay added.  Just before cal­en­der­ing, a fine spray of water is applied — bring­ing the clay to the sur­face — and it is this that forms the high sur­face.