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. This paper has a rough surface as the name suggests. The Rough sheet has been pressed between the "felts" on the paper machine and the roughness of the felt (blanket) is embossed into the wet sheet.