On tubes, labels and colour cards the lightfastness of Royal Talens products is indicated by the following symbols: +++ = at least 100 years lightfast under museum conditions ++ = at least 25 - 100 years lightfast under museum conditions + = at least 10 - 25 years lightfast under museum conditions º = at least 0 - 10 years lightfast under museum conditions These light fastnesses have been tested under museum conditions.