I have three jars of burnt sienna pigment purchased over the past years. They are also shown here in the pure form on the left with linseed added and on the right with lead white added. The Kremer pigment at the top is the lightest and has a distinct hot feel to it.
The Sinopia English variety is darker but still very warm. The one at the bottom is the oldest that I purchased maybe 20 to 25 years ago from an unknown supplier. It is the darkest and is almost black in hue with a warm reddish tone to it after the white is added. Burnt Siennas are endlessly useful on the palette. They can be used for warming black, the dark shadow side of red objects, in fleshtones, for backgrounds, in foliage, and all sorts of applications.