Derwent Lightfast pencils are oil-based, smooth and creamy and 100% lightfast. They feature a new design of core that is resistant to prolonged color change, ensuring your artwork will not fade for up to 100 years under museum conditions. The thick core gives a dense color application which brings vibrancy to any drawing. All colors comply with international lightfast testing standard, ASTM D-6901. pdf CC_ derwent_lightfast Derwent Lightfast color Chart.