I love the painting "Blues." The shadow is great in being both like and paradoxically unlike the thing shadowed. I like the layers of space in this painting. Every element is simple and carefully chosen. "Curves and Square" is another favorite of mine. I like the way, again, that the shadow both reflects the shape of the thing shadowed and also does not in that it has a different shape of its own. I think here of Plato and his comments on reflections and shadows: how these are three removes from reality, as is also painting (and tragic plays...his real target). However, I am not happy with his negative attitude about shadows since they seem to reveal more than he is willing to admit, and Sultan's paintings intimate this. Yes, they are illusions but they are also complements of reality, and perhaps undercut our belief in it in a certain way. Shadows and images tell us about our ambiguous relation to reality, as do dreams (Freud's great insight). Schopenhauer once said that a philosopher should be able to see the world as if it were a dream. This is also probably true for shadows, to see the world as if it were shadows. Shadows and reflections have different effects. Reflections pretend to give us an exact duplicate of the surface appearance of a thing. Shadows never do that. They intimate and somewhat distort the object: they turn it into shades of gray and erase much of its three-dimensionality. In my book I talk about shadows on a sidewalk and how they seem to create another world. Shadows also create an aura of their own. There is more in these paintings than shadows, though. The colors in these paintings are gorgeous and rich (they are in egg tempera on parchment, which gives an overall Medieval or Renaissance effect, the parchment adds to the color effect by providing a kind of inner luminescence not available in the regular canvas backing). Sultan is very aware of what Heidegger in "The Origins of the Work of Art" calls the thingly nature of the things, and also of the thingly nature of the work of art.
In another painting, "Blue and Yellow" the blue recedes behind the rest of the painting reminding me of something said by Hans Hoffman to his students along the lines of, as soon as you place a color on the canvas you make a space. Although Sultan owes something to minimalist abstraction her version (or rather, her style) has a rich subtlety that is relatively rare in that tradition. What is funny and interesting about this painting is that the title does not even mention the brown slash that dominates the left of the canvas field and no doubt represents a piece of metal, the blue lines perhaps shadows that belong to it.
"Orange Rounds" is a complex painting that is much better seen in person. Still, from the web image, we can see that this close-up of industrial machinery includes a detailed rendering of a ball-like object in shades of gray and black that provides a similar kind of mystery to the one I found in the black square in "Curves and Square."
I may update these notes later with further comments since there is much more to discuss, including Sultan's textile works, her potato prints, and her little boxes of parchment abstractions. But you can get discussions of all of that in Ashley's articles, so I will leave it here for now.