Ultramarine Blue plots cooler and bluer than the more saturated French Ultramarine. Temperature aside, both blues have equal permanence, lightfastness and transparency. Ultramarine Blue is slightly less granular in concentrated washes. For less saturation, sedimentation and cost, use Ultramarine Blue straight, for vibrant crayon-like color or mixed with a cool red for dark, effective neutrals.
Ultramarine Blue and French Ultramarine both contain pigment PB29, but Ultramarine has a smaller pigment particle size and is slightly greener and cooler than French Ultramarine, which has a larger pigment particle size and is slightly redder and warmer.
