Turning a painting upside down while in-process helps the artist catch problems in symmetry and likeness. This is a trick also used by signature forgers, for it turns letters (or in the case of the painting, features like an eye or set of lips) into pure shape. When we see something right-side-up, we can fail to see where, for example, a flat spot on a circle is. When we turn it upside down, it's not too unlike letting the opposite hemisphere of the brain act as a second opinion. Then, the flat spot jumps out at us and we can round out the shape into a proper circle.
"Henri Matisse's Le Bateau hung in New York's Museum of Modern Art for 47 days in 1961 before someone noticed it was upside down."-- Snopes Message Board, via googling "matisse upside down"
Hot color portraits
In 1961 Matisse's Le Bateau hung upside-down for 2 months.
Portrait painter
No. He is famous for his intricate details and realistic portraits of people(faces, bodies)
Frances Huemer has written: 'Portraits' -- subject(s): Belgian Portrait painting, Catalogs, European Portraits, Portrait painting, Belgian, Portraits, European
Hans Holbein the younger traveled around painting portraits.
le bateau
"Henri Matisse's Le Bateau hung in New York's Museum of Modern Art for 47 days in 1961 before someone noticed it was upside down."-- Snopes Message Board, via googling "matisse upside down"
George Romney, born on December 26, 1734, was an English painter who was famous for painting portraits of prominent people of the time. George was not known for painting portraits of pets.
the production of portraits
Duncan Thomson has written: 'Sir Henry Raeburn 1756-1823' -- subject(s): Painters, Biography 'Painting in Scotland, 1570-1650' -- subject(s): Biography, Exhibitions, Modern Painting, Painting, Modern, Painting, Scottish, Portrait painting, Scottish, Portraits, Portraits, Scottish, Scottish Painting, Scottish Portrait painting, Scottish Portraits 'Arikha' -- subject(s): Criticism and interpretation, Catalogs 'Avigdor Arikha'
Marcella Baur-Callwey has written: 'Die Differenzierung des Gemeinsamen' -- subject(s): English Portrait painting, Group Portraits, Men, Portrait painting, English, Portraits, Portraits, Group
My best guess is Marc Chagall, the Jewish Russian painter - I know of one painting of his that included an upside-down train, chuffing away.
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Frida Kahlo
Marie Antoinette