Dewent Lightfast pencils have been foemulated to be 100% lightfast. The revolutionary core is resistant to prolonged colour change ensuring artwork will not fade for up to 100 years under museum conditions. It's smooth oil base creates a rich vibrancy and can be mixed on the page to create a paint - like effect. Made from the finest raw materials and the purest pigments, all colours comply with internationally reconised lightfast testing standards ASTM D6901 and Blue Wool Scale ISO 105