cm). Challenges include the type of paint used to paint outdoors, animals, bugs, onlookers, and environmental conditions such as weather. Acrylic paint may harden and dry quickly in warm, sunny weather, and it cannot be reused. On the opposite side of the spectrum is the challenge of painting in moist or damp conditions with precipitation. The advent of plein air painting predated the invention of acrylics. The traditional and well-established method of painting en plein air incorporates the use of oil paint. Advocates French impressionist painters such as Claude Monet, Camille Pissarro, Alfred Sisley, and Pierre-Auguste Renoir advocated plein air painting, and much of their work was done outdoors in the diffuse light of a large white umbrella. Claude Monet was an avid en plein air artist who deduced that to seize the closeness and likeness of an outside setting at a specific moment one had to be outside to do so rather than just paint an outside setting in their studio.<ref>Kleiner, F. S., Gardner's Art Through the Ages (15th ed.), Boston, Cengage Learning, 1915</ref> In the second half of the 19th century and beginning of the 20th century in Russia, painters such as Vasily Polenov, Isaac Levitan, Valentin Serov, Konstantin Korovin and I. E. Grabar were known for painting en plein air. But enthusiasts of plein air painting were not limited to the Old World. American impressionists too, such as those of the Old Lyme school, were avid painters en plein air. American impressionist painters noted for this style during this era included Guy Rose, Robert William Wood, Mary DeNeale Morgan, John Gamble, and Arthur Hill Gilbert. In Canada, the Group of Seven and Tom Thomson are examples of en plein air'' advocates. Notable artists (selected) Frédéric Bazille Henri Biva Ralph Wallace Burton Mary Cassatt Jack Cassinetto William Merritt Chase Eugène Chigot Robert Clunie John Constable Lovis Corinth William Didier-Pouget Rackstraw Downes Carl Eytel Francesco Filippini David Gallup Arthur Hill Gilbert Vincent van Gogh I. E. Grabar George Hetzel Winslow Homer George Inness Konstantin Korovin Henri Le Sidaner Isaac Levitan Theodore Lukits The Macchiaioli Marvin Mangus Frederick McCubbin Stanisław Masłowski Willard Metcalf Claude Monet Berthe Morisot Edgar Payne Robert Antoine Pinchon Camille Pissarro William Preston Phelps Vasily Polenov Pierre-Auguste Renoir Tom Roberts Guy Rose John Singer Sargent Valentin Serov Alfred Sisley Matthew Smith Joaquín Sorolla Edward Stott Arthur Streeton Anthony Thieme Tom Thomson Henry Scott Tuke Andrew Winter Robert