Blockx French Ultramarine Blue Deep 15ml Watercolor Tube French ultramarine blue deep no253 is a transparent warm slightly reddish blue wonderful for painting skies Blockx watercolor is made in belgium since 1865 by the blockx family, 5 generations of chemists. Highest quality pure pigments ensure maximum color strength and quality. Rare, tough pigments are thoroughly crushed, then coated in gum arabic and honey. Blockx has no hues, tints, fillers or transient or unstable (non lightfast) colors, such as alizarin crimson for example