Sennelier's special process for manufacturing extra fine watercolours involves the soaking of pigments in purified water before the grinding & mixing process can begin. The colours are then ground on granite grindstones in the traditional manner to achieve maximum fineness & optimum dispersion. Only the finest pure gum Arabic from Kordafan mixed with glycerine is used as a binder for al intensely pigmented colours. Although the cornerstone of the range was developed in 1893, there have been recent additions of modern pigement types to provide enhanced lightfastness & stability. 10ml