Blockx, Watercolor Paint, Light Siena - Giant Tube. The range of extra-fine watercolors from Blockx consists of 72 vibrant shades, all of which exhibit an exceptionally high lightfastness (rating 7/8 on the international BWS measurement scale). The extra-fine watercolors from Blockx are primarily made from pure mono-pigments. No fillers or additives are included. The watercolors are composed of rare, finely ground pigments that are coated with gum arabic and honey to enhance the durability of the colors and give them more shine and brilliance. They offer a sheen and a creamy texture.