Densely worked in charcoal, his drawings resemble mezzotint prints, and they create a remarkable sculptural illusionism.
It is a "massive" freedom, she says, to work in charcoal and pastel rather than oil paint.
She works in charcoal on writing paper and never seals her drawings with a fixative, as if that would stifle them.
Hamilton also taught her to work with clay, and, with assistance, she produced objects in this medium and in watercolour, while working independently in charcoal, pastel, and pencil until 1984, when failing health forced her move to Santa Fe, where she died two years later.
Haefner started working in the 1930s, selling charcoal generators for heating houses.
The research from the two institutions, which have worked together on the Sunflowers since the 1990s, has revealed new details about the pigment Van Gogh used and how he planned the works in charcoal.
Within a short time she had abandoned engraving for illustration, and her works in charcoal, oil, watercolour, and other media became regular features in magazines such as Century, Cosmopolitan, and Harper's Weekly.
Gotting's eerie work in charcoal, which Sans Titre exhibited earlier this year, is full of mystery and shadow; the original artwork was priced from about $290, about average for a Sans Titre exhibition.
At Shepherd & Derom (58 East 79th Street), Margot Gordon offers a judicious eclecticism that ranges from a sprightly ink drawing of two putti by Raphael to a strangely Symbolist-looking work in charcoal, chalk and ink from 1984-85 by the Arte Povera artist Giuseppe Penone.
