In the long term, this ensures the paper maintains its colour without yellowing and will not embrittle with age. This is achieved by using fibres which are free from acidic elements and are treated in a neutral sizing system. The gelatine results in a brighter water colour wash as the colour sits on the surface. It makes liftingcolour easier and prevents masking fluid from damaging the paper surface. Water colour papers are traditionally white, this allows the maximum amount of light to be reflected back through the wash, giving that characteristic water colour 'sparkle'.
Tinted papers are sometimes preferred and give a mellow tone to a painting.
The heavier the sheet, the less the paper will cockle and the more costly it will be. The right side of the paper is the side from which you can read the watermark. However, either side of the paper can be used for painting. If you prefer the reverse, try to avoid the water mark area as it may interfere visually if the viewer can read the watermark backwards through your work. The right paper for you will usually be based upon your personal preference for a particular surface, closely followed by the colour of the sheet and last but not least, the weight.