Conservator, Laura Neufeld: O’Keeffe was very intentional about the materials that she used and she chose them to exploit inherent qualities of each one, like the velvety sootiness of charcoal, the rich, matte color of pastel, the luminosity of watercolor.
You see her using a vine charcoal, which is very splintery and powdery. She’s coupling that with fabricated charcoals that are much richer and come in different hardnesses. She’s getting just the absolute most out of a stick of charcoal in the range of tone that she achieves, in lights and darks, to get those beautiful gradations.
Pastels are really just made of a ground pigment then it’s combined with gum to hold that powdery pigment together into a stick form. She uses pastels from many different manufacturers because each one is going to have a slightly different blend of binder to pigment to make it harder or brighter. And then she got into making materials herself. So that might be making a pastel that’s bigger so she can cover more space with it.
In watercolor, you just see her reveling in that liquidity and how it’s pooling on the paper, how colors bleed together, and you can start to understand what might have made her pick a certain medium and pair it with a certain paper and make a certain composition.