Artists for many years have appreciated the qualities of the Langton. The paper is colour stable, mould made and acid free. The best watercolour papers are acid free to prevent the deterioration of paints and to preserve the integrity of the paper over time.- 12 sheets 300gsm (140lb) acid free watercolour paper. The surface of a Not (Cold Pressed) paper has a moderate texture. A Not sheet gets its name from 'not hot pressed'! It is made by taking a rough sheet and pressing it again without the felts. Not papers are generally considered the easiest to use.