A freshly-cleaned fashion statement by Édouard Manet goes back on view at the Solomon R. Guggenheim Museum in New York today (29 June) for the summer, after three years of research and restoration. The free and expressive brushstrokes and bright colours of Woman in Striped Dress (around 1877-80), a full-length portrait of an unidentified model—and of the dress itself—were hidden under two layers of discoloured varnish.

“Especially towards the end of his life, [Manet] was really quite modern in the way that he approached the canvas and he would describe things with very few touches,” says Lena Stringari, the deputy director and chief conservator of the Guggenheim Foundation, who led the project. “As this very thick and unsightly varnish came off, you could see how just with a few little touches he could make something sing.”

The major restoration was carried out to prepare for the work’s inclusion in the travelling exhibition Van Gogh to Picasso: the Thannhauser Legacy, due to open at the Guggenheim Bilbao on 21 September (until 24 March 2019), which includes the entire group of avant-garde late 19th- and early 20th-century works from the collection of the dealer Justin K. Thannhauser owned by the Guggenheim Museum. Several works in the collection were extensively researched in preparation for the show.

The late-period painting, found in the artist’s studio when he died, had been dramatically changed over the years, including being cut down on the sides and trimmed at the top, as is demonstrated by a photograph taken by Fernard Lochard in a studio inventory. Overpainting included an added signature (“Ed Manet”) and filling in the trellis-like background, which was less “finished”. The syrupy top, dark layer of varnish is a type typically used for musical instruments or wood furniture, also muted the painting’s sketchy energy. Even the subject’s right eyebrow was changed during the earlier restoration from a raised arch to a more neutral and passive line. These changes were presumably to make the painting more saleable, Stringari says.

The restoration and research project, which involved over 25 specialists, including scientists and art and fashion historians, began with intensive scientific analysis, including x-ray fluorescence, infrared reflectology and Raman spectroscopy. This revealed that there was no preparatory sketching underneath and the composition was not altered, suggesting “a remarkably direct and confident execution”, according to the catalogue entry by the Guggenheim senior curator Vivien Green and Gillian McMillan, the associate chief conservator for the collection.

McMillan’s gradual removal of most of the varnish, initially using very thin, small pieces of tissue for control, revealed not only the artist’s brushwork—“one of the most exciting things” for Stringari—but also that the dress is not black-and-white striped, but a greyish-white and black with deep blue-violet. Whether the unveiling will cause another viral dress sensation awaits to be seen.