When examining paper, a printer can look at four dimensions –
- General quality: this is the colour, look-through, finish and strength
- 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.