Question: The orientation found strongest early on in the movement of Rivera, Orozco, and Siqueiros all avowed communists is what?
About the article "Mexican muralism", section "Artistry".

Candidate passages:
Mario Orozco Rivera (b. January 19, 1930 – d. November 20, 1998 was a Mexican muralist and painter, a later proponent of Mexican muralism, and whose work was particularly influenced by David Alfaro Siqueiros.
He created a number of murals, mostly in the state of Veracruz before becoming an assistant to Siqueiros, directing the Taller Siqueiros in Cuernavaca and working with the artists on projects such as the Polyforum Cultural Siqueiros.
While preferring mural work, which he considered less commercial, Orozco Rivera also created oils and sculptures.
Many of these works were exhibited in Mexico and abroad and can be found in many major collections.
His work received recognition in various countries. 
Mexican populist art production from the 1920s to the 1950s is often grouped under the name of “Escuela Mexicana de Pintura (y Escultura) (Mexican School of Painting and Sculpture), coined in the 1930s by art historians and critics.
The term is not well-defined as it does not distinguish among some important stylistic and thematic difference, there is no firm agreement which artists belong to it nor if muralism should be considered part of it or separate.
It is not a school in the classic sense of the word as it includes work by more than one generation and with different styles that sometimes clash.
However, it does involve a number of important characteristics.
Mexican School mural painting was a combination of public ideals and artistic aesthics “positioned as a constituent of the official public sphere.” Three formal components of official Mexican muralism are defined as:1) Direct participation in official publicity and discourse2) Reciprocal integration of the visual discourse of the mural to an array of communicative practices participant in defining official publicity (including a variety of scriptural genres, but also public speech, debate and provocative public “event”)3) The development and public thematizing of a social-realist aesthetic (albeit multiform in character) as the visual register for the public sense of the mural work and as the doxic, or unquestioned, limits for public dispute over the representational space of the mural imageMost painters in this school worked in Mexico City or other cities in Mexico, working almost uninterrupted on projects and/or as teachers, generally with support of the government.
Most were concerned with the history and identity of Mexico and politically active.
Most art from this school was not created for direct sale but rather for diffusion in both Mexico and abroad.
Most were formally trained, often studying in Europe and/or in the Academy of San Carlos.
A large quantity of murals were produced in most of the country from the 1920s to 1970, generally with themes related to politics and nationalism focused often on the Mexican Revolution, mestizo identity and Mesoamerican cultural history.
These served as a form of cohesion among members of the movement.
The political and nationalistic aspects had little directly to do with the Mexican Revolution, especially in the later decades.
The goal was more to glorify it and its results as a means to legitimatize the post Revolution government.
The other political orientation was that of Marxism, especially class struggle.
This was strongest in the early movement with Rivera, Orozco and Siqueiros all avowed communists.
The political messages became less radical but they remained firmly to the left.
Much of the mural production glorified the indigenous aspect of Mexican culture, considering it an important factor in the creation of modern Mexico.
This was added with the idea of reexamining the country’s history from a different perspective.
One other aspect that most of the muralists shared was a rejection of the idea that art was only for the elite, but rather as a benefit for the masses.
The murals took on monumental status because of where they were situated, mostly on the walls of colonial era government buildings and the themes that were painted.
The mural painters of Mexico freely shared ideas and techniques as they were a closely knit group.
However, the work of each was distinctive as the government did not set style and artists can generally be deduced without looking at signatures.
Techniques included the revival of old techniques such as the fresco, painting on freshly plastered walls and encaustic or hot wax painting .
Others used mosaics and high fire ceramics, as well as metal parts, and layers of cement.
The most innovative of the artists was Siqueiros who worked with pyroxlene, a commercial enamel and Duco (used to paint cars), resins, asbestos, old machinery and was one of the first to use airbrush for artistic purposes.
He pored, sprayed, dripped and splattered paint for the effects they created haphazardly.
Although many have said that Siqueiros' artistic ventures were frequently “interrupted” by his political ones, Siqueiros himself believed the two were intricately intertwined.
By 1921, when he wrote his manifesto in "Vida Americana", Siqueiros had already been exposed to Marxism and saw the life of the working and rural poor while traveling with the Constitutional Army.
In "A New Direction for the New Generation of American Painters and Sculptors," he called for a "spiritual renewal" to simultaneously bring back the virtues of classical painting while infusing this style with "new values" that acknowledge the “modern machine” and the “contemporary aspects of daily life".
The manifesto also claimed that a "constructive spirit" is essential to meaningful art, which rises above mere decoration or false, fantastical themes.
Through this style, Siqueiros hoped to create a style that would bridge national and universal art.
In his work as well as his writing, Siqueiros sought a social realism that at once hailed the proletariat peoples of Mexico and the world while avoiding the clichés of trendy "Primitivism" and "Indianism".
In 1922, Siqueiros returned to Mexico City to work as a muralist for Álvaro Obregón’s revolutionary government.
Then Secretary of Public Education José Vasconcelos made a mission of educating the masses through public art and hired scores of artists and writers to build a modern Mexican culture.
Siqueiros, Rivera and José Orozco worked together under Vasconcelos, who supported the muralist movement by commissioning murals for prominent buildings in Mexico City.
Still, the artists working at the Preparatoria realized that many of their early works lacked the "public" nature envisioned in their ideology.
In 1923 Siqueiros helped found the Syndicate of Revolutionary Mexican Painters, Sculptors and Engravers, which addressed the problem of widespread public access through its union paper, "El Machete".
That year the paper published – "for the proletariat of the world" – a manifesto, which Siqueiros helped author, on the necessity of a "collective" art, which would serve as "ideological propaganda" to educate the masses and overcome bourgeois, individualist art.
Soon after, Siqueiros painted his famous mural "Burial of a Worker" (1923) in the stairwell of the Colegio Chico.
The fresco features an indigenous woman mourning over a coffin, decorated with a hammer and sickle.
But as the union became ever more critical of the revolutionary government, which had not instituted the promised reforms, its members faced new threats to cut funding for their art and the paper.
A feud within the union over whether to cease publishing "El Machete" or lose financial support for the mural projects left Siqueiros at the forefront, as Rivera left in protest of the decision to uphold politics over artistic opportunity.
Despite being let go from his post under the Department of Education in 1925, Siqueiros remained deeply entrenched in labor activities, in the union as well as the Mexican Communist Party, until he was jailed and eventually exiled in the early 1930s.
Siqueiros would paint "América Tropical" above what is now La Placita Olvera in Downtown Los Angeles on October 9, 1932.
It was poorly received and criticized for its political and social message.
It was whitewashed soon thereafter.
Eighty years later, The Getty Conservation Institute conserved and restored the mural.
It became accessible to the public on its 80th birthday, October 9, 2012.
No known color photographs of América Tropical are known to exist so conservators used scientific analysis and best practices to get at the artist's vision of his piece. 
By far, the three most influential muralists from the 20th century are Diego Rivera, José Clemente Orozco and David Siqueiros, called “los tres grandes” (the three great ones).
All believed that art was the highest form of human expression and a key force in social revolution.
Their work defined the movement taking over from Vasconcelos.
It created a mythology around the Mexican Revolution and the Mexican people which is still influential to this day, as well as promote Marxist ideals.
At the time the works were painted, they also served as a form of catharsis over what the country had endured during the war.
However, the three were different in their artistic expression.
Rivera’s works were utopian and idealist, Orozco’s were critical and pessimistic and the most radical were those of Siqueiros, heavily focused on a scientific future.
The differences among the three have much to do with how each experienced the Mexican Revolution.
Rivera was in Europe the entire time and did not fight.
He never depicted the horrors of the war but what he perceived to be the social benefits from it.
The other two did and both did express the horrors of war in their work.
There was resentment to Rivera by the other two because of it, especially from Siqueiros.
Of the three, Rivera was the most traditional in terms of painting styles, drawing heavily from European modernism.
In his narrative mural images, Rivera incorporated elements of cubism His themes were Mexican, often scenes of everyday life and images of ancient Mexico.
He originally painted this in bright colors in the European style but modified it to more earthy tones to imitate indigenous murals.
His greatest contribution is the promotion of Mexico’s indigenous past into how many people both inside and outside of the country view it.
Orozco also began with a European style of expression.
However his art developed into an angry denunciation of oppression especially by those he considered to be an evil and brutal rules class.
His work was somber and dire, with emphasis on human suffering and fear of the technology of the future.
His work shows an "expressionist use of color, slashing lines, and parodic distortions of the human figure."
Like most other muralists, Orozco condemned the Spanish as destroyers of indigenous culture, but he did have kinder depictions such as that of a Franciscan friar tending to an emaciated indigenous period.
Unlike other artists, Orozco never glorified the Mexican Revolution, having fought in it, but rather depicted the horrors of this war.
It caused many of his murals to be heavily criticized and even defaced.
Siqueiros was the youngest and most radical of the three.
He joined the Venustiano Carranza army when he was eighteen and experienced the Revolution from the front lines.
Although all three muralists were communists, Siqueiros was the most dedicated, as evidenced by his portrayals of the proletarian masses.
His work is also characterized with rapid, sweeping, bold lines and the use of modern enamels, machinery and other elements related to technology.
His style showed a "futurist blurring of form and technique."
His fascination with technology as it relates to art was exemplified when he emphasized the mass communications visual technology of photograph and motion picture in his eventual movement toward neorealism.
His radical politics made him unwelcome in Mexico and the United States, so he did much of his work in South America.
However, his masterpiece is considered to be the Polyforum Cultural Siqueiros, located in Mexico City.
The Big Three struggled to express their leftist leanings after the initial years painting murals under government supervision.
These struggles with the post-revolution government lead the muralists to create a union of artists and produce a radical manifesto.
The Secretary of Public Education under Obregon contracted Rivera, Siqueiros, and Orozco to pursue painting with the moral and financial support of the new post-revolutionary government.
Vasconcelos, while seeking to promote nationalism and “raza cosmica,” seemed to contradict this sentiment as he guided the muralists to create works in a classic, European style.
The murals became a target of Vasconcelos’s criticism when the Big Three departed from classical proportion and figure.
Siqueiros was dissatisfied with the incongruity between the murals and the revolutionary concerns of the muralists, and he advocated discussion among the artists of their future works.
In 1922 the muralists founded the Union of Revolutionary Technical Workers, Painters, and Sculptors of Mexico.
The Union then released a manifesto listing education, art of public utility, and beauty for all as the social goals of their future artistic endeavors. 
José Clemente Orozco, Fernando Leal, David Siqueiros and Diego Rivera the famous Mexican artists, renewed the art of fresco painting in the 20th century.
Orozco, Siqueiros, Rivera and his wife Frida Kahlo contributed more to the history of Mexican fine arts and to the reputation of Mexican art in general than anybody else.
Together with works by Orozco, Siqueiros, and others, Fernando Leal and Rivera's large wall works in fresco established the art movement known as "Mexican Muralism".
Among contemporary artists, Fernando Leal Audirac has developed a technique of transportable frescos.